Again, I would highlight the important points of the question.
Jodie buys 12 cans which are 330ml in each can.
Rob buys 4 bottles which are 1 litre each.
From 1), we can figure out how many ml Jodie bought. 12 x 330 = 10 x 330 + 2 x 330 = 3300 + 660 = 3960ml
From 2) we can figure out how many litres Rob bought. 4 x 1 = 4 litres.
However, to compare we would want both to be in litres or both to be in ml. We know that in 1 litre, there's 1000ml.
So if I convert Rob's 4 litres into ml, I would get 4 x 1000 = 4000ml.
Then to find out how much more Rob has than Jodie, I would subtract 4000 from 3960.
4000 - 3960 = 40ml.
If you decided to convert Jodie's 3960ml to litres, you would have to divide 3960 by 1000.
3960/1000 = 3.960.
Then you would take away. 4 - 3.960 = 0.04 litres which is also equal to 40ml.
Therefore, the answer is 40ml or 0.04 litres.