Plz need help last homework of the year

The number of revolutions of two pulleys is inversely proportional to their diameters. if a 24-inch diameter pulley making 400 revolutions per minute is belted to an 8-inch diameter pulley, find the number of revolutions per minute of the smaller pulley.

Look at the following graph of the given equation. determine whether the equation is a function. explain why or why not.

What is the best way to answer questions with a x expression in the question. for example 3x + 10x=?