The base of a parallelogram is 18 inches longer than three times the height. The area of the parallelogram is 216 square inches. What is the height?

12 inches

Step-by-step explanation:

Let b represent the base

h represents the height

area of the parallelogram = base * height = 216 square inches

From the question'

b = 18 + 3h

Slot in the value of b

216 = (18 + 3h) * h

expand

216 = 18h + 3h^2

subtract 216 from both sides

0 = 18h + 3h^2 - 216

rearrange

3h^2 + 18h - 216 = 0

divide through by 3

h^2 + 6h - 72 = 0

Now, lets solve!

h^2 + 6h - 12h - 72 = 0

h( h + 6 ) - 12(h + 6) = 0

(h - 12) (h + 6) = 0

h - 12 = 0

h = 12

and

h + 6 = 0

h = - 6

Taking the positive value of h

Hence, the height is 12 inches

Lets check

when h = 12 inches

Area of the parallelogram = 18* 12 = 216 square inches     correct

when h = -6inches

A = 18 * -6 ≠  216 square inches

So height is 12 inches