The probability that a student is absent given the day is Friday is 0.15. It has to be determined what the probability is of the student being absent and it being a Friday.
If P(A and B) is the probability of both event A and event B occurring, P(B|A) is the probability of B occurring if A has already occurred and P(A) being the probability of A occurring. P(B|A) = P(A and B)/P(A)
Here, the probability of a student being absent given the day is Friday is 0.15. P(B|A) = 0.15. Assuming that the school is closed on Saturday and Sunday, the probability of the day being Friday is 1/5.
This gives the probability that a student is absent and the day is Friday as 0.15*0.2 = 0.03
The probability that a student is absent and it is a Friday is 0.03.