An equation is two expressions separated by an equal sign. The key to solving equations is to 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.

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.

(4a)(5ab) - (9a²)(3b)
(4 x 5)(a x a x b) - (9 x 3)(a² x b)
(20)(a¹⁺¹ x b) - (27)(a²b)
20a²b - 27a²b
-7a²b

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.

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

a = l x w
a = a x b
a = 7 x 8
a = 56

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 < sign and the answer on the other.

-b - 4 < -8 + 7b
-b < -8 + 7b + 4
-b - 7b < -8 + 4
-8b < -4
b < \( \frac{-4}{-8} \)
b < \(\frac{1}{2}\)