Question 128616
L=W+3 
2L+2W=78
2(W+3)+2W=78
2W+6+2W=78
4W=78-6
4W=72
W=72/4
W=18 IS THE WIDTH.
L=18+3=21 IS THE LENGTH.
PROOF:
2*18+2*21=78
36+42=78
78=78