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

y² - 11y + 18 = 0
(y - 2)(y - 9) = 0

For this expression to be true, the left side of the expression must equal zero. Therefore, either (y - 2) or (y - 9) must equal zero:

If (y - 2) = 0, y must equal 2
If (y - 9) = 0, y must equal 9

So the solution is that y = 2 or 9

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

The volume of a cylinder is πr²h:

v = πr²h
v = π(4² x 5)
v = 80π

To solve this equation, repeatedly do the same thing to both sides of the equation until the variable is isolated on one side of the equal sign and the answer on the other.

-8z - 7 = -8 - 7z
-8z = -8 - 7z + 7
-8z + 7z = -8 + 7
-z = -1
z = \( \frac{-1}{-1} \)
z = 1

The circumference of a circle is the distance around its perimeter and equals π (approx. 3.14159) x diameter: c = π d. The area of a circle is π x (radius)² : a = π r².