The formula for perimeter is: P=2W+2L
Rewrite as: 2W = P-2L
Divide all terms by 2: P/2-L=W
Width is 1/5p, replace W in the equation: P/2-L= 1/5P
Multiply each term by 10: 5P-10L=2P
Subtract 2p from both sides and add 10L to both sides: 3P=10L
Lenght is given as 15 inches, replace L with 15 and multiply: 3P=150
Divide both sides by 3: P=50
W=1/5P = 10 inches
