We are trying to figure out: (prob of driver in class A having an accident)/(prob of any driver having an accident). So we know the probability of some driver in class A, B, or C having an accident within the first year: (prob of being in class * prob of having accident) for each class. Sum those up to find the prob of any driver and you should be on the right track. Just remember when something is given that is the new denominator in the probability because you are only look at those people because it is already given that this event has happened.
Does this make sense? I got scolded the other day for giving too much of an answer away, so I am trying to help you without being to obvious or giving you the answer. Sorry if it came across as confusing.