def miles_per_gallon(start_miles, end_miles, amount_gallons):
    """Compute and return the average number of miles
    that a vehicle traveled per gallon of fuel.

    Parameters
        start_miles: An odometer value in miles.
        end_miles: Another odometer value in miles.
        amount_gallons: A fuel amount in U.S. gallons.
    Return: Fuel efficiency in miles per gallon.
    """
    distance = end_miles - start_miles
    mpg = distance / amount_gallons
    return mpg