4 bottles of 750 mm each
liters of 7Up
1 liter= 1000 mm
Then add, all botlles volumes,
4x750 + 1000= 4000 mm ,or 4 liters of punch
Then ,difference of orange and 7Up is
4x750 - 1000= 3000- 1000 = 2000
Is a mix of 3 parts of juice,and 1 part of 7Up
So then answer is
Difference between both= 2000 mm
. = 2 liters