Question 578879
Form a right triangle:

L=w+2  

let a=w, b=w+2 and c=18

a^2+b^2=c^2

w^2 + (w+2)^2 = 18^2

w^2 + w^2 +4w + 4 = 324

2w^2 + 4w + 4 = 324

2w^2 + 4w - 320 = 0

*[invoke quadratic "x", 2, 4, -320 ]

Thus it is roughly 11.69 x 13.69