Answer
length = width + 15
Area = length * width; area is 54 square feet.
Two equations are:
L = W + 15
L * W = 54
To solve, we substitute first equation into second equation:
(W + 15) * W = 54
w^2 + 15w = 54
w^2 + 15w - 54 = 0
(w+18)(w-3) = 0
w = -18 or 3
The width cannot be negative, so 3 is the width and since length is 15 more than width, length is 18:
Length = 18 feet
Width = 3 feet
