The volume of a triangular prism is the "area of a triangle" times the "thickness." The area of a triangle is (base times height) over 2. V = ((b*h)/2)*T Given V = 2400 cu. cm, b = 16 cm, T = 20 cm, and h is unknown, h = (2V)/(bL) = (2*2400)/(16*20) = 15 cm
Note that the given 17 cm in the picture is useless.