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.

5a - 2a = 3a

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 - 1)(y - 8)
(y x y) + (y x -8) + (-1 x y) + (-1 x -8)
y² - 8y - y + 8
y² - 9y + 8

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.

(3a)(2ab) - (8a²)(3b)
(3 x 2)(a x a x b) - (8 x 3)(a² x b)
(6)(a¹⁺¹ x b) - (24)(a²b)
6a²b - 24a²b
-18a²b

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.

6a x 9b = (6 x 9) (a x b) = 54ab

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.

9a⁹ - 6a⁹ = 3a⁹