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.

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 equal sign and the answer on the other.

2z - 9 = \( \frac{z}{-7} \)
-7 x (2z - 9) = z
(-7 x 2z) + (-7 x -9) = z
-14z + 63 = z
-14z + 63 - z = 0
-14z - z = -63
-15z = -63
z = \( \frac{-63}{-15} \)
z = 4\(\frac{1}{5}\)

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.

(8a)(3ab) - (7a²)(4b)
(8 x 3)(a x a x b) - (7 x 4)(a² x b)
(24)(a¹⁺¹ x b) - (28)(a²b)
24a²b - 28a²b
-4a²b

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.

6a + 7a = 13a

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(7 + 6)(3)
a = ½(13)(3)
a = ½(39) = \( \frac{39}{2} \)
a = 19\(\frac{1}{2}\)