Ok so volume is 3 times so you could use paper or a calculator but basically you would have to multiply all of them so 10.4 x 5 x 8 is what you have to do and when you get that your done it is very simple hope it helps
What you need to do is to find a multiple of 20 and 16 in other words a number that can multiply into 20 and 16. You have 2 and you have 4. So now this is how it looks like.
