Jeff put a small box that is 12 inches long 8 inches wide and 4 inches tall inside a box that is 20 inches long 15 inches wide and 19 inches height how much space is left in the larger box

So what you need to do is take the volume of the smaller box from the larger box, and you will be left with the volume of the space. Like so:

Large Box
20 x 15 x 19
= 5700
Small Box
12 x 8 x 4
= 384
Take one away from the other
5700 - 384
= 5316

Hope this helps!
- Z

Volume of the 1st box =12x8x4 =384 in³

Volume of the 2nd box =20x15x19 =5,700 in³

Volume left = 2nd Volume - 1st Volume ==>5,700 - 384 = 5,316 in³