The perimeter of a rectangle is 104 cm. The length is 12 cm more than the width. Find the length and the width.

So L = W + 12

And the perimeter is given by

P = 2( W + L)  = 2(W + W + 12) = 2(2W + 12)   so we have

104cm =2(2W + 12)     divide both sides by 2

52cm = 2W + 12          sobtract 12 from both sides

40cm = 2W       divide by 2 on both sides

20cm = W     and the Length is 12 more = 32cm