12 out of 16 Ohio House seats went Republican. Ohio was 50/50 between Romney and Obama approximately.
Assume the only crossovers are GOP voting Obama.
(Amazing, I thought we were all racist)
Anyhow, 3/4 of state was GOP, and 1/4 of all voters were GOP crossovers.
What percentage of GOP voters were crossovers?
We take 1/4 over 3/4 to get 1/3.
So we learn fractions.