The formula for the conditional probability is as follows:

where P(A|B) is the probability of A given B, P(A∩B) is the probability of A and B, and P(B) is the probability of B. Note that P(A∩B)=P(B∩A).
In the given problem, we have the following:

where A stands for athlete and B stands for biology major.
Thus, for P( biology major | athlete), we have the following:

For P(athlete | biology major), we have the following:
