Question 513636
Let:  L=Length and W=Width
Perimeter = 2L + 2W
W = L – 12 … width 12 units less than length
108 = 2L + 2(L-12) 
108 =2L + 2L - 24
108 = 4L - 24
108 + 24 = 4L -24 + 24
132 = 4L
132/4 = 4L/4
33 = L