Which model is NOT a function? (i accidentally clicked on b ignore that lol)

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.

Use the quadratic function to predict f(x) if x equals 8. f(x) = 25x2 − 28x + 585

Solve the system of equations using the linear combination method. {4x−3y=127x−3y=3 enter your answers in the boxes.