Question 332700
the pond is 20 by 15
..

let the border width be x
..
so the width including border will be 15+2x  ( x on either side)
The length including width = 20+2x
..
Area of entire plot including border = 500 sq.ft= (15+2x)(20+2x)
..
4x^2+70x+300=500
4x^2+70x-200=0
4x^2+80x-10x-200=0
4x(x+20)-10(x+20)=0
(x+20)(4x-10)=0
4x-10=0
4x=10
x=10/4
x= 2.5 feet.
..
CHECK
(15+5)*(20+5)= 500