Answer:
16x^2 + 8x.
Explanation:
To find the area of the walkway, you need to do the area of the whole thing minus the area of the pool.
The area of the whole thing is (8x - 3)(2x + 7) = 16x^2 - 6x + 56x - 21 = 16x^2 + 50x - 21.
The area of the pool is (8x - 3 - x - x)(2x + 7 - x - x) = (6x - 3)(7) = 42x - 21.
So, the area of the walkway is 16x^2 + 50x - 21 - (42x - 21) = 16x^2 + 50x - 21 - 42x + 21 = 16x^2 + 8x.
If you want, you can factor that and make it 8x(2x + 1).
Hope this helps!