You can work this several ways. One way is to figure out how many stickers each has, then write their relationship as a ratio.
Here, Lisa will have 12/2 = 6 more than half the total number of stickers, hence 36. John will have the remaining 24. Their ratio is
Lisa's stickers : John's stickers = 36 : 24 = 3 : 2
Another way to look at this is to realize 12 divides 60 into 5 equal parts. The ratio that will total 5 parts with one number being 1 larger than the other is 3 : 2.
Lisa's stickers : John's stickers = 3 : 2
