Question 313705
let the width be x
The length will be x+20
The area = 500 sq.ft
..
area = L*W
x(x+20)=500
x^2+20x=500
x^2+20x-500=0
..
x1 , x2 the roots have to be found out.
x1=-20+sqrt(20^2+4*1*500) /2
x1=14.49 
x2=-40-sqrt(40^2+4*1*500) /2
=--34.49
..
width =14.49 feet
length = 500/14.49
=34.5 feet