Which expression is equivalent to 510•55

Someone me! if you’re smart you can solve this!

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?

What three-dimensional solid have 6 rectangular faces, 2 equal bases that are not rectangles and 18 edges