Question 655227
A man built a walk of uniform width around a rectangular pool. If the area of the walk is 115 square feet and the dimensions of the pool are 15 feet by 3 feet, how wide is the walk? 
.
Area of pool:
15*3 = 45 square feet
.
Area of pool and walk:
(x+15)(x+3) = x^2+18x+45
.
"area of walk" = "area of pool and walk" - "area of walk"
115 = x^2+18x+45 - 45
115 = x^2+18x
0 = x^2+18x-115
0 = (x+23)(x-5)
x = {-23, 5}
throw out the negative solution (extraneous) leaving
x = 5 feet