The first step to solve a quadratic equation that's set to zero is to factor the quadratic equation:

y² - 5y - 36 = 0
(y + 4)(y - 9) = 0

For this expression to be true, the left side of the expression must equal zero. Therefore, either (y + 4) or (y - 9) must equal zero:

If (y + 4) = 0, y must equal -4
If (y - 9) = 0, y must equal 9

So the solution is that y = -4 or 9

To solve this equation, replace the variables with the values given and then solve the now variable-free equation. (Remember order of operations, PEMDAS, Parentheses, Exponents, Multiplication/Division, Addition/Subtraction.)

8b(b - y)
8(-8)(-8 - 2)
8(-8)(-10)
(-64)(-10)
640

The surface area of a cube is (2 x length x width) + (2 x width x height) + (2 x length x height):

sa = 2lw + 2wh + 2lh
sa = (2 x 9 x 4) + (2 x 4 x 2) + (2 x 9 x 2)
sa = (72) + (16) + (36)
sa = 124

A trapezoid is a quadrilateral with one set of parallel sides.

A cube is a rectangular solid box with a height (h), length (l), and width (w). The volume is h x l x w and the surface area is 2lw x 2wh + 2lh.