To multiply monomials, multiply the coefficients (the numbers that come before the variables) of each term, add the exponents of like variables, and multiply the different variables together.

(5a)(3ab) - (9a²)(8b)
(5 x 3)(a x a x b) - (9 x 8)(a² x b)
(15)(a¹⁺¹ x b) - (72)(a²b)
15a²b - 72a²b
-57a²b

An exterior angle of a triangle is equal to the sum of the two interior angles that are opposite:

d° = b° + c°

To find angle c, remember that the sum of the interior angles of a triangle is 180°:

180° = a° + b° + c°
c° = 180° - a° - b°
c° = 180° - 49° - 59° = 72°

So, d° = 59° + 72° = 131°

A shortcut to get this answer is to remember that angles around a line add up to 180°:

a° + d° = 180°
d° = 180° - a°
d° = 180° - 49° = 131°

The volume of a cube is height x length x width:

v = h x l x w
v = 3 x 4 x 9
v = 108

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 4 x 4) + (2 x 4 x 4) + (2 x 4 x 4)
sa = (32) + (32) + (32)
sa = 96

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

z² + 14z + 45 = 0
(z + 5)(z + 9) = 0

For this expression to be true, the left side of the expression must equal zero. Therefore, either (z + 5) or (z + 9) must equal zero:

If (z + 5) = 0, z must equal -5
If (z + 9) = 0, z must equal -9

So the solution is that z = -5 or -9