A right angle measures 90 degrees and is the intersection of two perpendicular lines. In diagrams, a right angle is indicated by a small box completing a square with the perpendicular lines.

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.

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)(9ab) + (3a²)(8b)
(3 x 9)(a x a x b) + (3 x 8)(a² x b)
(27)(a¹⁺¹ x b) + (24)(a²b)
27a²b + 24a²b
51a²b

A rhombus is a parallelogram with four equal-length sides. A square is a rectangle with four equal-length sides.

The area of a trapezoid is one-half the sum of the lengths of the parallel sides multiplied by the height:

a = ½(b + d)(h)
a = ½(4 + 7)(3)
a = ½(11)(3)
a = ½(33) = \( \frac{33}{2} \)
a = 16\(\frac{1}{2}\)