Aboat travels 105 km downstream in 5 hours. the return trip upstream takes 7 hours. find the speed of the boat in still water and the speed of the current.

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?