Triangles and Polygons

Question

A designer is creating a rectangular travel board game. The width of the board is to be 9 inches shorter than the length. If the surface area of the board will be 112 square inches, what will be the length, in inches, of the board?

Answer 1

surface area of rectangular board is length * width

l = length

w = length - 9 = l - 9

area = 112

112 = l * (l-9)

112 = l^2 - 9l

l^2 - 9l - 112 = 0

(l - 16)(l + 7) = 0

l = 16

w = l - 9 = 7

Answer 2

112 = x(x - 9)

Can you solve for x and answer?