Question 233868
L=12W
P=84
P=2L+2W
84=2(12w)+2w
84=24w+2w 
84=26W
84/26=W
3.231=W ANS. FOR THE WIDTH.
L=12*3.231=38.76 ANS. FOR THE LENGTH
PROOF:
84=2*38.77+2*3.23
84=77.54+6.46
84=84