What is the first term of the quotient of the following division problem?

There are three bags: a (contains 2 white and 4 red balls), b (8 white, 4 red) and c (1 white 3 red). you select one ball at random from each bag, observe that exactly two are white, but forget which ball came from which bag. what is the probability that you selected a white ball from bag a?

Rose bought a new hat when she was on vacation. the following formula describes the percent sales tax rose paid b=t-c/c

Which one is the correct answer, and why?