Question 328135
Comment: W=8-L is not the same as W=L-8
.
Let L=length, w=width and P=perimeter
2L+2w=P
2L+2w=96
.
3w=L-8
L=3w+8 
.
2(3w+8)+2w=96 Substitution
6w+16+2w=96
8w=80
w=10 m
L=38 m
.
Ed