8.5 is the same as 8.50, right? So just take the digit in the hundredth place of both decimals and subtract. You'd be doing 0-4 so you can go ahead and borrow a number to make 10-4, which equals 6. So without subtracting 8.5 and 4.64, you can determine that 6 will be in the hundredth place. Hope this helps!
1/5 of a litre is 0.2 litres
1 litre minus 0.2 litres is 0.8 litres so
0.8 divided by 5 (glasses) is 0.16 litres in each glass
