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

p = x + y + z
p = 14cm + 7cm + 9cm = 30cm

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.

(2a)(7ab) + (6a²)(5b)
(2 x 7)(a x a x b) + (6 x 5)(a² x b)
(14)(a¹⁺¹ x b) + (30)(a²b)
14a²b + 30a²b
44a²b

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° - 70° - 55° = 55°

So, d° = 55° + 55° = 110°

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° - 70° = 110°

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.

A trapezoid is a quadrilateral with one set of parallel sides.