Question 882284
The sum of the areas of the new parking lot and the sidewalk is 60*80 square feet.


New lot area is {{{(2/3)(60*80)}}}.
The parking lot area is also shorter in both dimensions by 2 times the width w of the sidewalk.  The factor 2, because each dimension has two ends.  Try drawing a picture to help see.


{{{highlight_green((60-2w)(80-2w)=(2/3)*(60*80))}}}
{{{4800-160w-120w+4w^2=4800}}}
{{{4w^2-280w+4800=4800}}}
{{{4w^2-280w=0}}}
{{{w^2-70=0}}}
{{{w^2=70=7*2*5}}}
{{{highlight(w=sqrt(70))}}}


<b>8 feet 4 inches</b> plus maybe 3/8 inch