P = perimeter
Perimeter of a rectangle = l + l + w + w
or P = 2l + 2w
You know:
P = 150 m
l = w + 5 [length is 5 m greater than the width]
P = 2l + 2w Plug in what you know
150 = 2(w + 5) + 2w Simplify, distribute/multiply 2 into (w + 5)
150 = 2w + 10 + 2w
150 = 4w + 10 Subtract 10 to both sides of the equation
140 = 4w Divide 4 on both sides
35 = w
PROOF l = w + 5 ---> l = 40
P = 2l + 2w
150 = 2(40) + 2(35)
150 = 80 + 70
150 = 150