Answer
The width of the pool is $23$ meters, and the length is $40$ meters.
Work Step by Step
Let the width of the pool be $ w.$
We are told that the length is $2w-6.$
The perimeter equals 2$\times $(width + length)
=$2(w+2w-6)=2(3w-6)=6w-12$
Given $\quad 6w-12=126\qquad $ ... add 12
$ 6w=138\qquad $ ... divide with 6
$ w=23$ meters
The width of the pool is $23$ meters, and the length is $2(23)-6=40$ meters.
