Using quadratic equation functions

Question

A rectangle has a length of 12 feet less than 3 times its width, if the area of the rectangle is 180 square feet find the length of the rectangle.

Answer 1

L = 3W - 12

LW = 180

(3W-12)W = 180

3W^2 -12W = 180

W^2 -4W = 60

W^2 -4W -60 =0

(W -10)(W+6) = 0

W = 10 feet

L = 18 feet

18=3(10) -12

10x18 = 180 ft^2