There are 12 governor seats up for reelection. there are only 2 candidates in each race--democrats and republicans and the each have an equal shot at winning.
What is the probability that half of the seats are won by democrats and half are won by republicans?
Each candidate has a 1/2 chance of winning or losing....but I can't seem to line this answer up.
Look up the binomial distribution on Wikipedia. It will tell you everything you need to know about the binomial distribution.