let L = the length and W = the width of the rectangle. According the problem we have L = 3W
so the area of the rectangle is A = 3W*W = 3W^2 cm^2
if we decrease the two dimentions of the rectangle by 2, we will have (L-2)(W-2) = 3W^2 -36
substituting on the first side where L = 3W the first side becomes; (3W-2)(W-2) = 3W^2 - 6W - 2W + 4 -->>
3w^2 - 8W + 4 = 3W^2 - 36 --->>> -8W = -40 --->>> W = 5 cm and L = 15 cm ( because L=3W)
So the area is 3*5^2 = 3*25 = 75 cm^2 or 5*15 = 75 cm^2
check (5-2)(15-2) = 3*13 = 39 and this is 36 less than 75