Answer:
H= 15 inches
Explanation:
You know the volume is: V = L * W * H
You know the length and the width, therefore
18 * 12 * H = 3240
216H = 3240
H = 3240/216
H = 15 inches is the height of the tank
You can make sure it is right:
18 * 12 * 15= 3240