Question 1150910
w, the width of the patio border

Pool "area",  {{{40*60}}}

Border area, {{{(40+2w)(60+2w)-40*60}}}


The pool area is given as equal to the border area.
{{{40*60=(40+2w)(60+2w)-40*60=40*60}}}
.
.
{{{50w+w^2=600}}}

{{{w(w+50)=600}}}------you could try to see if whole numbers will work.



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10 & 60 will work.
{{{highlight(w=10)}}}