percentage_calculator.py

def percent_of(x: float, y: float) -> float:
    return (x / 100) * y


def what_percent_of(x: float, y: float) -> float:
    return (x / y) * 100


def percent_change(x: float, y: float) -> float:
    return ((y - x) / x) * 100


x = 10
y = 100
print(percent_of(x, y))

x = 166
y = 1006
print(what_percent_of(x, y))

y = 90
x = 100
print(percent_change(x, y))