Given the formula A=(20−2x)(15−2x), what does (15−2x) represent in this context?

Question

A rectangular pool surrounded by a walkway is enclosed in a backyard. The enclosed section covers an area of 300 square feet, and the width is 5 feet shorter than the length. The walkway has width  feet.

1. the width in feet of the enclosed section, including the pool and walkway
2. the length in feet of the enclosed section, including the pool and walkway
3. the width of the pool in feet
4. the length of the pool in feet

Answer 1

the width of the pool in feet, that' the 3rd choice

15-2x is 5 feet shorter than 20-2x, just as the width is 5 less than the length. 20-2x is the length.

they're also each 2x less than the length and width of the section which includes pool and walkway.

so each is the length and width of just the pool, in feet