Final test of the year :) PLZZZ help

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?

Write 5(6x+4)-2(5x-2) in the form a(bx+c) where a,b and c integers and a> 1

Use sigma notation to represent the following series for 9 terms.