To find the height of the triangle you will use the formula to find the area of the triangle and the information provided about the area and the base length.
A= 1/2 bh
558 = 1/2 x 36 x h
558 = 18 x h
To solve for the height divide both sides by 18.
This leaves you with 31 = h.
So, the height is 31 inches.
