Divide 252 by 21. 21 times 12 = 252 12 is 9 units shorter than 21. so the answer is 12 inches by 21 inches you work backwards from the area area = width times length a = wl we know w is 9 units shorter than the length so now we have the equation 252=(l-9) times l plug in 21 for l and then solve there is your answer.
