We could do long division for polynomials, but it's easier to use the remainder theorem when we're dividing by a monic first degree expression.
The remainder when we divide polynomial f(x) by x-a is f(a)
f(4) = 4(4)^3-20(4)^2+18(4)-12 = 256 - 320 + 72 - 12 = -4
Answer: Remainder -4
