Answer:
The width of the tank is approximately 7.9 feet.
Explanation:
The pool is a rectangular prism with the following dimensions:
length = 2*x feet
width = x feet
height = 4 feet
With volume equal to 500 cubic feet, therefore:
volume = length*width*height = 500
(2*x)*(x)*(4) = 500
8*x² = 500
x = sqrt(500 / 8)
x = sqrt(62.5)
x = 7.90569 feet
The width of the tank is 7.9 feet.