Answer:
6 cm
Explanation:
Volume of a Prism = base area x height = 
Base area = length x width = 12 x 2 = 24 cm^2
Volume = 24 x 3 = 72 cm^3
Volume of a pyramid = 1/3( l x w x h) 
72 = 1/3( 6x6 x h) 
Multiply both sides of the equation by 3
216 = 36 x h 
divide both sides by 36
h = 6