Answer:
1 yard
Step-by-step explanation:
If x is the width of the deck, then its area is the sum of the areas along each side and the areas of the squares in the four corners. The area along the sides is the product of x and the perimeter of the pool, which is 2(8+10) = 36 yards.
40 = 36x +4x^2
10 = 9x +x^2 . . . . . . divide by 4
x^2 +9x -10 = 0 . . . . put in standard form
(x -1)(x +10) = 0 . . . . . factor
The positive value of x that makes this true is x=1.
The width of the deck is 1 yard.
