Answer:
30 feet by 18 feet
Step-by-step explanation:
Area = length * width
A = x*w
w = x - 12
A = 540 sq. ft
540 = x * (x -12)
x*x - 12x - 540 = 0
x*x - 12x + 36 - 36 - 540 = 0
(x - 6)^2 - 576 = 0
x - 6 = 24
or x -6 = -24
x = 30 or x = -18
w = 30 - 12 = 18
30 ft by 18 ft
