probabilities and likelihoods problem

can anyone explain to me how to do this problem?

Assume that a person who is trying to rate a movie has a critical nature, so that her prior probabilities for a movie to be good or bad are p(G)=1/10 and p(B)=9/10. Further, suppose the likelihoods for good or bad reviews are asymmetric: p(+|G)=2/3, but p(-|B)=3/4. If this individual observes two good reviews, find her posterior probability the movie is good, p(G|++). Compute this probability two ways: first using two updating steps, (i.e. something along the lines of p(G|+) and p(B|-)), then in one-step, using the likelihoods p(--|G) and p(--|B). How do the results compare?
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