To multiply binomials, use the FOIL method. FOIL stands for First, Outside, Inside, Last and refers to the position of each term in the parentheses:

(y + 7)(y - 9)
(y x y) + (y x -9) + (7 x y) + (7 x -9)
y² - 9y + 7y - 63
y² - 2y - 63

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° - 22° - 58° = 100°

So, d° = 58° + 100° = 158°

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° - 22° = 158°

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 6 x 1) + (2 x 1 x 5) + (2 x 6 x 5)
sa = (12) + (10) + (60)
sa = 82

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)(4ab) - (3a²)(6b)
(5 x 4)(a x a x b) - (3 x 6)(a² x b)
(20)(a¹⁺¹ x b) - (18)(a²b)
20a²b - 18a²b
2a²b

Angles around a line add up to 180°. Angles around a point add up to 360°. When two lines intersect, adjacent angles are supplementary (they add up to 180°) and angles across from either other are vertical (they're equal).