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Answer:
A = 4x² +60x
Explanation:
The area of walkway along each of the sides is the product of side length and walk width x. The total for the four sides is ...
12x + 18x + 12x + 18x = 2x(12 +18) = 60x
There is a square of walkway at each corner whose dimensions are x by x, so the corner area is ...
4·x²
Then the total walkway area is ...
A = 4x² +60x