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The outside dimensions of the large rectangle are 30+2x by 40+2x feet
and its area is the product (30+2x)*(40+2x) square feet.
The pool's dimensions are 30 by 40 feet, and its area is 30*40 square feet.
The area of the pathway is the DIFFERENCE of these areas
(30+2x)*(40+2x) - 30*40.
It is the expression you are looking for.
Solved, answered and explained.
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