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.

(9a)(2ab) + (6a²)(5b)
(9 x 2)(a x a x b) + (6 x 5)(a² x b)
(18)(a¹⁺¹ x b) + (30)(a²b)
18a²b + 30a²b
48a²b

You can only add or subtract monomials that have the same variable and the same exponent. For example, 2a + 4a = 6a and 4a² - a² = 3a² but 2a + 4b and 7a - 3b cannot be combined. However, you can multiply and divide monomials with unlike terms. For example, 2a x 6b = 12ab.

The entire length of this line is represented by AD which is AB + BD:

AD = AB + BD

The perimeter of a triangle is the sum of the lengths of its sides:

p = x + y + z
p = 8cm + 14cm + 15cm = 37cm

For parallel lines with a transversal, the following relationships apply:

• angles in the same position on different parallel lines equal each other (a° = w°, b° = x°, c° = z°, d° = y°)
• alternate interior angles are equal (a° = z°, b° = y°, c° = w°, d° = x°)
• all acute angles (a° = c° = w° = z°) and all obtuse angles (b° = d° = x° = y°) equal each other
• same-side interior angles are supplementary and add up to 180° (e.g. a° + d° = 180°, d° + c° = 180°)

Applying these relationships starting with z° = 18, the value of a° is 18.