When solving an equation with two variables, 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.)

A line segment is a portion of a line with a measurable length. The midpoint of a line segment is the point exactly halfway between the endpoints. The midpoint bisects (cuts in half) the line segment.

The first step to solve a quadratic expression that's not set to zero is to solve the equation so that it is set to zero:

z² + 3z - 15 = -3z + 1
z² + 3z - 15 - 1 = -3z
z² + 3z + 3z - 16 = 0
z² + 6z - 16 = 0

Next, factor the quadratic equation:

z² + 6z - 16 = 0
(z - 2)(z + 8) = 0

For this expression to be true, the left side of the expression must equal zero. Therefore, either (z - 2) or (z + 8) must equal zero:

If (z - 2) = 0, z must equal 2
If (z + 8) = 0, z must equal -8

So the solution is that z = 2 or -8

Perimeter is equal to the sum of the four sides:

p = a + b + c + d
p = 8 + 6 + 4 + 7
p = 25

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 2 x 2) + (2 x 2 x 5) + (2 x 2 x 5)
sa = (8) + (20) + (20)
sa = 48