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(8 + 9)(4)
a = ½(17)(4)
a = ½(68) = \( \frac{68}{2} \)
a = 34

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)(5b)
(3 x 9)(a x a x b) + (3 x 5)(a² x b)
(27)(a¹⁺¹ x b) + (15)(a²b)
27a²b + 15a²b
42a²b

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.

-7a - 9 = \( \frac{a}{-4} \)
-4 x (-7a - 9) = a
(-4 x -7a) + (-4 x -9) = a
28a + 36 = a
28a + 36 - a = 0
28a - a = -36
27a = -36
a = \( \frac{-36}{27} \)
a = -1\(\frac{1}{3}\)

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 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.

2a - 9a = -7a