add two number and return them

Here's a simple function in Python that adds two numbers and returns their sum:

```python
def add_numbers(a, b):
    """
    Adds two numbers and returns their sum.

    Args:
        a (float): The first number.
        b (float): The second number.

    Returns:
        float: The sum of a and b.
    """
    return a + b

# Example usage:
num1 = 5
num2 = 7
result = add_numbers(num1, num2)
print(f"The sum of {num1} and {num2} is: {result}")
```

This function takes two arguments `a` and `b`, adds them together, and returns the result. The example usage demonstrates how to call the function with two numbers and print the result.