Question

You are fencing a rectangular puppy kennel with 25 ft. of fence. The side of the kennel against your house does not need a fence. This side is 9 ft. long. Find the dimensions of the kennel.

Answer 1

w = width
l = length = 9
Perimeter = 2*w+2*l
Normally you would face the whole perimeter but "the side of the kennel against your house does not need a fence." So you actually fence 2*w+1*l

2w+l=25
2w+9=25
2w=16
w=8

The dimensions  of the kennel are:
w=8 ft
l=9ft