let w stand for the width, then length = w+3 (3 more than width)
area is length times width. in terms of w, area = w(w+3)
know that area = 180
so w(w+3) = 180
distribute on the left w^2 + 3w = 180
set = 0 and factor w^2 + 3w - 180 = 0
(w-12)(w+15) = 0
so w = 12 or -15
it must be 12 since you can't have a negative length.
therefore w = 12 and length = w+3 = 15
rectangle is 12 x 15 cm