assignment 3 solution

[RichoKD]

Added subtraction, multiplication and division to utils

pub fn sub_u8(x: u8, y: u8) -> u8{
    x - y
}

pub fn multiply_u8(x: u8, y: u8) -> u8{
    x * y
}

pub fn divide_u8(x: u8, y: u8) -> u8{
    x / y
}