1 liter of mixture contains 5 parts of gasoline and 1 part of oil. so we have a total of 6 parts. so each part
is 1000 ml / 6 parts = 166.66 ml / part
let x is the quantity of gasoline we must add in the mixture to make a mixture of 23 parts of gasoline
and 1 part of oil. So it will be x + 5 * 166.66 = (x + 833.33) parts of gasoline and 1 part of oil
so it should be (x + 833.33) / 166.66 = 23 so x + 833.33 = 3833.18 so x = 3833.18 - 833.33 = 2999.85 ml
So 2999.85 ml of gasoline should be added in the mixture to get a mixture of 23 parts of gasoline to 1 part of oil.
Check; we have 2999.85 ml + 833.33 ml = 3833.18 ml of gasoline / 166.66 ml of oil = 23 this is the ratio
of parts of gasoline to parts of oil.