Jeff put a small box that is 12 inches long, 8inches wide, and 4 inches tall inside a box that is 20 inches long, 15 inches wide and 9 inches high. how much space is left in the larger box?

Formula 

V is H×L×W
small box details are 12 inches long, 8 inches wide, and 4 inches tall therefore using the formula given, 12 × 8 × 4 gives you 384 inches ³
big box details are 20 inches long, 15 inches wide, and 9 inches high there using the formula given, 20 × 15 × 9 gives you 2700 inches ³
cubed to the 3rd? because there are 3 numbers instead of 2
so, you're left to subtract with what you gotten 2700 - 384 gives you 2316 inches cubed. hope that was helpful