diff --git a/exercises/binary_search_recursive/solution.py b/exercises/binary_search_recursive/solution.py
index c437af8..97235c5 100644
--- a/exercises/binary_search_recursive/solution.py
+++ b/exercises/binary_search_recursive/solution.py
@@ -1,11 +1,21 @@
-SUBMIT = False
+SUBMIT = True
 
 
 def binary_search_recursive(
-    lst: list[int], target: int, low: int = 0, high: int | None = None
+    lst: list[int], target: int, low: int = 0, high: int = None
 ) -> int:
     """Recursive Binary Search"""
-    pass
+    if high == None:
+        high = len(lst)
+    
+    while low < high:
+        mid = (low + high) // 2
+        if lst[mid] < target:
+            return binary_search_recursive(lst, target, mid+1, high)
+        elif lst[mid] > target:
+            return binary_search_recursive(lst, target, low, mid)
+        return mid
+    return -1
 
 
 def test() -> None:
diff --git a/exercises/case_inverter/solution.py b/exercises/case_inverter/solution.py
index 4f8a5db..dc573fa 100644
--- a/exercises/case_inverter/solution.py
+++ b/exercises/case_inverter/solution.py
@@ -1,19 +1,20 @@
-SUBMIT = False
+SUBMIT = True
 
 
 def case_inverter(s: str) -> str:  # noqa: ARG001
     """
     Inverts the case of each character in a string.
     """
-    inverted_s = ""
+    new_s = ''
     for char in s:
-        if char.islower():
-            inverted_s += char.upper()
-        elif char.isupper():
-            inverted_s += char.lower()
+        if char.isalpha():
+            if char.islower():
+                new_s += char.upper()
+            else:
+                new_s += char.lower()
         else:
-            inverted_s += char
-    return inverted_s
+            new_s += char
+    return new_s  
 
 
 def test() -> None:
@@ -21,8 +22,8 @@ def test() -> None:
     cases = [
         ("Hello World!", "hELLO wORLD!"),
         ("", ""),
-        ("all lower", "ALL UPPER"),
-        ("ALL UPPER", "all lower"),
+        ("all lower", "ALL LOWER"),
+        ("ALL UPPER", "all upper"),
         ("1234567890 !@#$%^&*()", "1234567890 !@#$%^&*()"),
         ("Python 3.12", "pYTHON 3.12"),
     ]
diff --git a/exercises/celsius_to_fahrenheit/solution.py b/exercises/celsius_to_fahrenheit/solution.py
index fedf347..4012911 100644
--- a/exercises/celsius_to_fahrenheit/solution.py
+++ b/exercises/celsius_to_fahrenheit/solution.py
@@ -1,19 +1,12 @@
-SUBMIT = False
+SUBMIT = True
 
 
 def celsius_to_fahrenheit(_celsius: float) -> float:
     # noqa: ARG001
-    """Converts Celsius to Fahrenheit using the formula: F = (C * 9/5) + 32.
-
-    Example usage:
-    >>> celsius_to_fahrenheit(0)
-    32.0
-    >>> celsius_to_fahrenheit(100)
-    212.0
-    >>> celsius_to_fahrenheit(-40)
-    -40.0
-    """
-    return 0.0
+    """Converts Celsius to Fahrenheit using the formula: F = (C * 9/5) + 32."""
+    
+    F = (_celsius * 9/5) + 32
+    return F
 
 
 def test() -> None:
diff --git a/exercises/char_frequency/solution.py b/exercises/char_frequency/solution.py
index 3a45f7f..a529101 100644
--- a/exercises/char_frequency/solution.py
+++ b/exercises/char_frequency/solution.py
@@ -1,12 +1,16 @@
-SUBMIT = False
+SUBMIT = True
 
 
 def char_frequency(s: str) -> dict[str, int]:
     """Counts the frequency of each character in a string."""
-    counts = {}
+    if not s:
+        return {}
+    
+    d = {}
     for char in s:
-        counts[char] = counts.get(char, 0) + 1
-    return counts
+        d.setdefault(char, 0)
+        d[char] += 1
+    return d
 
 
 def test() -> None:
diff --git a/exercises/count_vowels/solution.py b/exercises/count_vowels/solution.py
index e03c7cf..2b36a42 100644
--- a/exercises/count_vowels/solution.py
+++ b/exercises/count_vowels/solution.py
@@ -1,6 +1,14 @@
 import ast
 from pathlib import Path
 
+def count_vowels(s: str) -> int:
+    vowels = {'a', 'e', 'i', 'o', 'u', 'A', 'E', 'I', 'O', 'U'}
+    count = 0
+    for char in s:
+        if char in vowels:
+            count += 1
+    return count
+
 def test_exercise_solutions_have_asserts() -> None:
     """Verify that all exercise solution stubs have a test() function with asserts."""
     root = Path(__file__).parent.parent
diff --git a/exercises/factorial_iterative/solution.py b/exercises/factorial_iterative/solution.py
index 78bca9d..1e2fa84 100644
--- a/exercises/factorial_iterative/solution.py
+++ b/exercises/factorial_iterative/solution.py
@@ -1,18 +1,14 @@
-SUBMIT = False
+SUBMIT = True
 
 
 def factorial_iterative(_n: int) -> int:
     # noqa: ARG001
-    """Calculates n! using a loop.
-
-    Example usage:
-    >>> factorial_iterative(0)
-    1
-    >>> factorial_iterative(5)
-    120
-    """
-    return 0
-
+    """Calculates n! using a loop."""
+    f = 1
+    while _n > 0:
+        f *= _n
+        _n -= 1
+    return f
 
 def test() -> None:
     """Simple self-test for Iterative Factorial."""
diff --git a/exercises/factorial_tail/solution.py b/exercises/factorial_tail/solution.py
index e661ccc..a3ce695 100644
--- a/exercises/factorial_tail/solution.py
+++ b/exercises/factorial_tail/solution.py
@@ -1,9 +1,11 @@
-SUBMIT = False
+SUBMIT = True
 
 
 def factorial_tail(n: int, acc: int = 1) -> int:
     """Tail Recursive Factorial"""
-    pass
+    if n == 0:
+        return acc
+    return factorial_tail(n-1, acc=acc*n)
 
 
 def test() -> None:
diff --git a/exercises/fast_exponentiation/solution.py b/exercises/fast_exponentiation/solution.py
index 596fd5a..dfd8760 100644
--- a/exercises/fast_exponentiation/solution.py
+++ b/exercises/fast_exponentiation/solution.py
@@ -1,9 +1,15 @@
-SUBMIT = False
+SUBMIT = True
 
 
 def fast_exponentiation(a: int, n: int) -> int:
     """Fast Exponentiation"""
-    pass
+    if n == 0:
+        return 1
+    elif n % 2 == 0:
+        b = fast_exponentiation(a, n//2)
+        return b * b
+    elif n % 2 == 1:
+        return a * fast_exponentiation(a, n-1)
 
 
 def test() -> None:
diff --git a/exercises/fibonacci/solution.py b/exercises/fibonacci/solution.py
index b85766d..6e4eda3 100644
--- a/exercises/fibonacci/solution.py
+++ b/exercises/fibonacci/solution.py
@@ -1,25 +1,19 @@
-SUBMIT = False
+SUBMIT = True
 
 
 def fibonacci(n: int) -> int:
-    """Calculates the n-th Fibonacci number.
-
-    Example usage:
-    >>> fibonacci(0)
-    0
-    >>> fibonacci(1)
-    1
-    >>> fibonacci(5)
-    5
-    >>> fibonacci(10)
-    55
-    """
-    return 0
+    """Calculates the n-th Fibonacci number."""
+    
+    if n == 0:
+        return 0
+    elif n == 1:
+        return 1
+    return fibonacci(n-1) + fibonacci(n-2)
 
 
 def test() -> None:
     """Simple self-test for Fibonacci."""
-    cases = {0: 0, 1: 1, 5: 5, 10: 55}
+    cases = {0: 0, 1: 1, 5: 5, 10: 55, 30: 832040}
     for n, expected in cases.items():
         try:
             res = fibonacci(n)
diff --git a/exercises/fibonacci_tail/solution.py b/exercises/fibonacci_tail/solution.py
index 1dbb03b..e2f5886 100644
--- a/exercises/fibonacci_tail/solution.py
+++ b/exercises/fibonacci_tail/solution.py
@@ -1,9 +1,15 @@
-SUBMIT = False
+SUBMIT = True
 
 
 def fibonacci_tail(n: int, a: int = 0, b: int = 1) -> int:
     """Tail Recursive Fibonacci"""
-    pass
+    if n == 0:
+        return a
+    elif n == 1:
+        return b
+    
+    c = a+b
+    return fibonacci_tail(n-1, b, c)
 
 
 def test() -> None:
@@ -11,6 +17,7 @@ def test() -> None:
     assert fibonacci_tail(0) == 0, f"Expected 0, got {fibonacci_tail(0)}"
     assert fibonacci_tail(5) == 5, f"Expected 5, got {fibonacci_tail(5)}"
     assert fibonacci_tail(10) == 55, f"Expected 55, got {fibonacci_tail(10)}"
+    assert fibonacci_tail(50) == 12586269025, f"Expected 12586269025, got {fibonacci_tail(50)}"
     print("✅ All tests passed!")
 
 
diff --git a/exercises/hello_world/solution.py b/exercises/hello_world/solution.py
index 19b776e..e65fc9d 100644
--- a/exercises/hello_world/solution.py
+++ b/exercises/hello_world/solution.py
@@ -1,14 +1,8 @@
-SUBMIT = False
+SUBMIT = True
 
 
 def hello_world() -> str:
-    """Returns the string 'Hello, World!'.
-
-    Example usage:
-    >>> hello_world()
-    'Hello, World!'
-    """
-    return ""
+    return 'Hello, World!'
 
 
 def test() -> None:
diff --git a/exercises/linear_search/solution.py b/exercises/linear_search/solution.py
index ad4cb38..d21c6b6 100644
--- a/exercises/linear_search/solution.py
+++ b/exercises/linear_search/solution.py
@@ -1,18 +1,12 @@
-SUBMIT = False
+SUBMIT = True
 
 
 def linear_search(_items: list[int], _target: int) -> int:
-    """Find the first index of a target value in a list.
-
-    Example usage:
-    >>> linear_search([10, 20, 30, 40, 50], 30)
-    2
-    >>> linear_search([1, 2, 3, 4, 5], 10)
-    -1
-    >>> linear_search([], 5)
-    -1
-    """
-    return 0
+    """Find the first index of a target value in a list."""
+    for index, element in enumerate(_items):
+        if element == _target:
+            return index
+    return -1
 
 
 def test() -> None:
diff --git a/exercises/list_average/solution.py b/exercises/list_average/solution.py
index 48fdf47..2620325 100644
--- a/exercises/list_average/solution.py
+++ b/exercises/list_average/solution.py
@@ -1,16 +1,14 @@
-SUBMIT = False
+SUBMIT = True
 
 
 def list_average(_numbers: list[float]) -> float:
-    """Returns the mean of a numeric list.
-
-    Example usage:
-    >>> list_average([1, 2, 3, 4, 5])
-    2.5
-    >>> list_average([10, 20, 30])
-    20.0
-    """
-    return 0.0
+    """Returns the mean of a numeric list."""
+    
+    if not _numbers:
+        return 0
+    s = sum(_numbers)
+    l = len(_numbers)
+    return s / l
 
 
 def test() -> None:
diff --git a/exercises/list_mode/solution.py b/exercises/list_mode/solution.py
index 304c15a..a67b5ef 100644
--- a/exercises/list_mode/solution.py
+++ b/exercises/list_mode/solution.py
@@ -1,18 +1,22 @@
 from typing import Any
 
-SUBMIT = False
+SUBMIT = True
 
 
 def list_mode(_items: list[Any]) -> Any:
-    """Returns the most frequent element in a list.
-
-    Example usage:
-    >>> list_mode([1, 2, 2, 3, 3, 3])
-    3
-    >>> list_mode(['a', 'b', 'a'])
-    'a'
-    """
-    return None
+    """Returns the most frequent element in a list."""
+    if not _items:
+        return None
+    elements = {}.fromkeys(_items, 0)
+    
+    for item in _items:
+        elements[item] += 1
+    
+    num = max(elements.values())
+    
+    for key, value in elements.items():
+        if value == num:
+            return key
 
 
 def test() -> None:
diff --git a/exercises/matrix_add/solution.py b/exercises/matrix_add/solution.py
index 53deb25..17deab9 100644
--- a/exercises/matrix_add/solution.py
+++ b/exercises/matrix_add/solution.py
@@ -1,17 +1,23 @@
-SUBMIT = False
+SUBMIT = True
 
 
 def matrix_add(mat1: list[list[int | float]], mat2: list[list[int | float]]) -> list[list[int | float]]:
     """Adds two matrices."""
-    # Placeholder implementation
-    _ = mat1
-    _ = mat2
-    return []
+    mat3 = []
+    temp = [0] * len(mat1[0])
+    for i in range(len(mat1)):
+        mat3.append(temp)
+    
+    for x in range(len(mat1)):
+        for y in range(len(mat1[0])):
+            mat3[x][y] = mat1[x][y] + mat2[x][y]
+    
+    return mat3
 
 
 def test() -> None:
     """Simple self-test for Matrix Addition."""
-    cases = [(([1, 2], [3, 4]), [4, 6])]  # Example matrices
+    cases = [(([[1, 2]], [[3, 4]]), [[4, 6]])]  # Example matrices
     for input_data, expected in cases:
         try:
             res = matrix_add(*input_data)
diff --git a/exercises/matrix_mul/solution.py b/exercises/matrix_mul/solution.py
index 14f34cd..b03d2c8 100644
--- a/exercises/matrix_mul/solution.py
+++ b/exercises/matrix_mul/solution.py
@@ -1,6 +1,32 @@
 import ast
 from pathlib import Path
 
+def columna_i(mat, i):
+    columna = []
+    for fila in mat:
+        columna.append(fila[i])
+    return columna
+        
+def producto_escalar(fila_a, fila_b):
+    escalar = 0
+    for i in range(len(fila_a)):
+        escalar += fila_a[i] + fila_b[i]
+    return escalar
+        
+def matrix_mul(mat_a, mat_b):
+    columnas_b = len(mat_b[0])
+    mat_c = []
+    
+    for fila_a in mat_a:
+        fila_c = []
+        for i in range(columnas_b):
+            columna_b = columna_i(mat_b, i)
+            escalar = producto_escalar(fila_a, columna_b)
+            fila_c.append(escalar)
+        mat_c.append(fila_c)
+    return mat_c
+        
+
 def test_exercise_solutions_have_asserts() -> None:
     """Verify that all exercise solution stubs have a test() function with asserts."""
     root = Path(__file__).parent.parent
diff --git a/exercises/matrix_trace/solution.py b/exercises/matrix_trace/solution.py
index 8c1f733..7bc3786 100644
--- a/exercises/matrix_trace/solution.py
+++ b/exercises/matrix_trace/solution.py
@@ -1,4 +1,4 @@
-SUBMIT = False
+SUBMIT = True
 
 
 def matrix_trace(mat: list[list[int | float]]) -> int | float:
@@ -9,6 +9,7 @@ def matrix_trace(mat: list[list[int | float]]) -> int | float:
     return trace
 
 
+
 def test() -> None:
     """Simple self-test for Matrix Trace."""
     cases = [
diff --git a/exercises/min_max_list/solution.py b/exercises/min_max_list/solution.py
index fa46d23..81dfe33 100644
--- a/exercises/min_max_list/solution.py
+++ b/exercises/min_max_list/solution.py
@@ -1,18 +1,22 @@
-SUBMIT = False
+SUBMIT = True
 
 
 def min_max_list(_items: list[int]) -> tuple[int, int] | None:
-    """Find both min and max values in a list by iterating once.
-
-    Example usage:
-    >>> min_max_list([3, 1, 4, 1, 5, 9, 2, 6, 5])
-    (1, 9)
-    >>> min_max_list([10])
-    (10, 10)
-    >>> min_max_list([])
-    None
-    """
-    return (0, 0)
+    """Find both min and max values in a list by iterating once."""
+    
+    if not _items:
+        return None
+    
+    menor = _items[0]
+    mayor = menor
+    
+    for i in range(1, len(_items)):
+        if _items[i] < menor :
+            menor = _items[i]
+        if _items[i] > mayor:
+            mayor = _items[i]
+    
+    return (menor, mayor)
 
 
 def test() -> None:
diff --git a/exercises/palindrome/solution.py b/exercises/palindrome/solution.py
index 7664e28..7048bd0 100644
--- a/exercises/palindrome/solution.py
+++ b/exercises/palindrome/solution.py
@@ -1,17 +1,21 @@
-SUBMIT = False
+SUBMIT = True
 
 
 def palindrome(_text: str) -> bool:
     # noqa: ARG001
-    """Checks if a string is a palindrome.
-
-    Example usage:
-    >>> palindrome("racecar")
-    True
-    >>> palindrome("hello")
-    False
-    """
-    return False
+    """Checks if a string is a palindrome."""
+    new_text = []
+    for char in _text:
+        new_text.append(char)
+    i, j = 0, len(new_text)-1
+    
+    while i < j:
+        if new_text[i] != new_text[j]:
+            return False
+        i +=1
+        j -= 1
+    return True
+    
 
 
 def test() -> None:
diff --git a/exercises/personalized_greeting/solution.py b/exercises/personalized_greeting/solution.py
index aed3a12..18dbd35 100644
--- a/exercises/personalized_greeting/solution.py
+++ b/exercises/personalized_greeting/solution.py
@@ -1,17 +1,10 @@
-SUBMIT = False
+SUBMIT = True
 
 
 def personalized_greeting(_name: str, _age: int) -> str:
     # noqa: ARG001
-    """Returns a personalized greeting message.
-
-    Example usage:
-    >>> personalized_greeting("Alice", 25)
-    'Hello Alice, you are 25 years old'
-    >>> personalized_greeting("Bob", 30)
-    'Hello Bob, you are 30 years old'
-    """
-    return ""
+    """Returns a personalized greeting message."""
+    return f'Hello {_name}, you are {_age} years old'
 
 
 def test() -> None:
diff --git a/exercises/poly_add/solution.py b/exercises/poly_add/solution.py
index c6932aa..feb69b5 100644
--- a/exercises/poly_add/solution.py
+++ b/exercises/poly_add/solution.py
@@ -1,18 +1,27 @@
-SUBMIT = False
+SUBMIT = True
 
 
 def poly_add(poly1: list[int | float], poly2: list[int | float]) -> list[int | float]:
     """Adds two polynomials."""
-    _poly1 = poly1
-    _poly2 = poly2
-    # Placeholder implementation: Add actual logic here.
-    # For now, return an empty list to pass initial checks.
-    return []
-
+    
+    if len(poly1) < len(poly2):
+        temp = [0] * (len(poly2) - len(poly1))
+        temp.extend(poly1)
+        poly1 = temp
+        
+    elif len(poly2) < len(poly1):
+        temp = [0] * (len(poly1) - len(poly2))
+        temp.extend(poly2)
+        poly2 = temp
+    
+    new_poly = []
+    for i in range(len(poly1)):
+        new_poly.append(poly1[i]+poly2[i])
+    return new_poly
 
 def test() -> None:
     """Simple self-test for Polynomial Addition."""
-    cases = [(([1, 2], [3, 4]), [4, 6]), (([1, 0, 1], [1, 1]), [1, 1, 1])]
+    cases = [(([1, 2], [3, 4]), [4, 6]), (([1, 0, 1], [1, 1]), [1, 1, 2])]
     for input_data, expected in cases:
         try:
             res = poly_add(*input_data)
diff --git a/exercises/poly_evaluate/solution.py b/exercises/poly_evaluate/solution.py
index b1c4db3..2b0f55b 100644
--- a/exercises/poly_evaluate/solution.py
+++ b/exercises/poly_evaluate/solution.py
@@ -1,13 +1,13 @@
-SUBMIT = False
+SUBMIT = True
 
 
 def poly_evaluate(poly: list[int | float], x: int | float) -> int | float:
     """Evaluates a polynomial at a given value x using Horner's method."""
-    result = 0
-    for coeff in reversed(poly):
-        result = result * x + coeff
-    return result
-
+    count = 0
+    for i in range(len(poly)-1, -1, -1):
+        count += poly[i] * (x**i)
+    
+    return count
 
 def test() -> None:
     """Simple self-test for Polynomial Evaluation."""
diff --git a/exercises/poly_mul/solution.py b/exercises/poly_mul/solution.py
index ee4fab3..aa6890f 100644
--- a/exercises/poly_mul/solution.py
+++ b/exercises/poly_mul/solution.py
@@ -1,12 +1,19 @@
-SUBMIT = False
+SUBMIT = True
 
 
 def poly_mul(poly1: list[int | float], poly2: list[int | float]) -> list[int | float]:
     """Multiplies two polynomials."""
-    _poly1 = poly1
-    _poly2 = poly2
-    # Placeholder implementation
-    return []
+    poly1.reverse()
+    poly2.reverse()
+    
+    grade = len(poly1) + len(poly2) - 1
+    new_poly = [0]*grade
+    
+    for i, num1 in enumerate(poly1):
+        for j, num2 in enumerate(poly2):
+            new_poly[i+j] += num1 * num2
+    new_poly.reverse()
+    return new_poly
 
 
 def test() -> None:
diff --git a/exercises/prefix_sums/solution.py b/exercises/prefix_sums/solution.py
index 1e3d167..e2a35ff 100644
--- a/exercises/prefix_sums/solution.py
+++ b/exercises/prefix_sums/solution.py
@@ -1,16 +1,15 @@
-SUBMIT = False
+SUBMIT = True
 
 
 def prefix_sums(_numbers: list[int]) -> list[int]:
-    """Returns the cumulative sums of a list.
-
-    Example usage:
-    >>> prefix_sums([1, 2, 3])
-    [1, 3, 6]
-    >>> prefix_sums([10, -10, 5])
-    [10, 0, 5]
-    """
-    return []
+    """Returns the cumulative sums of a list"""
+    numbers_sum = []
+    for i in range(len(_numbers)):
+        count = _numbers[i]
+        for j in range(i):
+            count += _numbers[j]
+        numbers_sum.append(count)
+    return numbers_sum
 
 
 def test() -> None:
diff --git a/exercises/prime_check/solution.py b/exercises/prime_check/solution.py
index 3cb981b..dc5a599 100644
--- a/exercises/prime_check/solution.py
+++ b/exercises/prime_check/solution.py
@@ -1,19 +1,19 @@
-SUBMIT = False
+SUBMIT = True
 
 
 def prime_check(_n: int) -> bool:
     # noqa: ARG001
-    """Checks if a number is prime.
-
-    Example usage:
-    >>> prime_check(2)
-    True
-    >>> prime_check(4)
-    False
-    >>> prime_check(17)
-    True
-    """
-    return False
+    """Checks if a number is prime"""
+    if _n == 0 or _n == 1:
+        return False
+    raiz = _n**(1/2)
+    
+    i = 2
+    while i <= raiz:
+        if _n%i == 0:
+            return False
+        i += 1
+    return True
 
 
 def test() -> None:
diff --git a/exercises/recursive_min_max/solution.py b/exercises/recursive_min_max/solution.py
index c9fcfce..aee4a5b 100644
--- a/exercises/recursive_min_max/solution.py
+++ b/exercises/recursive_min_max/solution.py
@@ -1,11 +1,22 @@
-SUBMIT = False
-
+SUBMIT = True
 
 def recursive_min_max(
     lst: list[int], low: int = 0, high: int | None = None
 ) -> tuple[int, int]:
     """Recursive Min/Max"""
-    pass
+    if high == None:
+        high = len(lst)
+    
+    if low == high-1:
+        min_value = lst[low]
+        max_value = min_value
+        return min_value, max_value
+    
+    mid = (low + high) // 2
+    min_value = min(recursive_min_max(lst, low, mid)[0], recursive_min_max(lst, mid, high)[0])
+    max_value = max(recursive_min_max(lst, low, mid)[1], recursive_min_max(lst, mid, high)[1])
+    
+    return min_value, max_value
 
 
 def test() -> None:
diff --git a/exercises/simple_interest/solution.py b/exercises/simple_interest/solution.py
index 944bc7f..81dd7f1 100644
--- a/exercises/simple_interest/solution.py
+++ b/exercises/simple_interest/solution.py
@@ -1,17 +1,10 @@
-SUBMIT = False
+SUBMIT = True
 
 
 def simple_interest(_principal: float, _rate: float, _time: float) -> float:
     # noqa: ARG001
-    """Calculates simple interest using the formula: I = (P * R * T) / 100.
-
-    Example usage:
-    >>> simple_interest(1000, 5, 2)
-    100.0
-    >>> simple_interest(500, 3.5, 1)
-    17.5
-    """
-    return 0.0
+    """Calculates simple interest using the formula: I = (P * R * T) / 100."""
+    return _principal * _rate * _time / 100
 
 
 def test() -> None:
diff --git a/exercises/string_reversal/solution.py b/exercises/string_reversal/solution.py
index 9f36e58..db7c773 100644
--- a/exercises/string_reversal/solution.py
+++ b/exercises/string_reversal/solution.py
@@ -1,13 +1,14 @@
-SUBMIT = False
+SUBMIT = True
 
 
 def string_reversal(s: str) -> str:  # noqa: ARG001
     """
     Reverses a string.
     """
-    # Add a basic assert to the stub to satisfy the test
-    assert True, "Placeholder assert for string reversal" # Placeholder assert
-    return ""
+    new_s = ''
+    for char in s:
+        new_s = char + new_s
+    return new_s
 
 
 def test() -> None:
diff --git a/exercises/sum_list_recursive/solution.py b/exercises/sum_list_recursive/solution.py
index d041b78..07d7759 100644
--- a/exercises/sum_list_recursive/solution.py
+++ b/exercises/sum_list_recursive/solution.py
@@ -1,4 +1,4 @@
-SUBMIT = False
+SUBMIT = True
 
 
 def sum_list_recursive(lst: list[int]) -> int:
diff --git a/exercises/sum_two_numbers/solution.py b/exercises/sum_two_numbers/solution.py
index 6bed6c8..894e77d 100644
--- a/exercises/sum_two_numbers/solution.py
+++ b/exercises/sum_two_numbers/solution.py
@@ -1,19 +1,10 @@
-SUBMIT = False
+SUBMIT = True
 
 
 def sum_two_numbers(_a: int, _b: int) -> int:
     # noqa: ARG001
-    """Returns the sum of two integers.
-
-    Example usage:
-    >>> sum_two_numbers(3, 4)
-    7
-    >>> sum_two_numbers(-1, 1)
-    0
-    >>> sum_two_numbers(0, 0)
-    0
-    """
-    return 0
+    """Returns the sum of two integers."""
+    return _a + _b
 
 
 def test() -> None:
diff --git a/exercises/variable_swap/solution.py b/exercises/variable_swap/solution.py
index cceb784..fb70377 100644
--- a/exercises/variable_swap/solution.py
+++ b/exercises/variable_swap/solution.py
@@ -1,17 +1,11 @@
 from typing import Any
 
-SUBMIT = False
+SUBMIT = True
 
 
 def variable_swap(a: Any, b: Any) -> tuple[Any, Any]:
-    """Swaps the values of a and b.
-
-    Example usage:
-    >>> variable_swap(5, 10)
-    (10, 5)
-    >>> variable_swap("hello", "world")
-    ('world', 'hello')
-    """
+    """Swaps the values of a and b."""
+    a,b = b,a
     return a, b
 
 
diff --git a/exercises/word_count/solution.py b/exercises/word_count/solution.py
index 41c9a8d..63240ad 100644
--- a/exercises/word_count/solution.py
+++ b/exercises/word_count/solution.py
@@ -1,9 +1,12 @@
-SUBMIT = False
+SUBMIT = True
 
 
 def word_count(s: str) -> int:
     """Counts the number of words in a string."""
-    return len(s.split())
+    
+    num = s.split()
+    num = len(num)
+    return num
 
 
 def test() -> None: