Since x is the length, then x+7 has to be the width. The area of a rectangle can be found via the formula : A = length * width So if we replace the area with the given number (170) and the length, and width, with what we assumed, we get.. 170 = x * (x+7) [which is.. ] 170 = x^2 +7x 0 = x^2 +7x - 170