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 - 9)(y + 8)
(y x y) + (y x 8) + (-9 x y) + (-9 x 8)
y² + 8y - 9y - 72
y² - y - 72

The area of a parallelogram is equal to its length x width:

a = l x w
a = a x b
a = 3 x 2
a = 6

To combine like terms, add or subtract the coefficients (the numbers that come before the variables) of terms that have the same variable raised to the same exponent.

7a - 2a = 5a

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.

2y + 5 = \( \frac{y}{-7} \)
-7 x (2y + 5) = y
(-7 x 2y) + (-7 x 5) = y
-14y - 35 = y
-14y - 35 - y = 0
-14y - y = 35
-15y = 35
y = \( \frac{35}{-15} \)
y = -2\(\frac{1}{3}\)

The sum of the interior angles of a triangle is 180°:
180° = a° + b° + c°
c° = 180° - a° - b°
c° = 180° - 47° - 61° = 72°