16.87
V=L times W times H*V=volume W=width H=heightand you don't actually have to write times you can do the symbol.
Example- if I had a rectangular prism of the width is 5 cubes, the length 8 cubes, and the height 7 cubes(following how many gallons are in a cube 7.5) I would then use my formula. V=LWH- 8 times 7= 56 56 times 5=280 280 times 7.5= 2100V=2100 (that is your answer reply If you didn't mean the volume or you don't get it)
hope it helps :)