Add the two parts of the 1:3 ratio: 1 + 3 = 4. Now divide 88 by 4:
88/4 = 22
One group gets 1*22 = 22 ballots. The other group gets 3*22 = 66 ballots. 22+66 = 88 so all of the ballots are accounted for and the ratio of the groups is:
22:66 = 1:3