Twice a number is 8 less than 3 times the number

3. find the radius of circle p.4. find y.

We just started the introduction into circles and i have no idea how to do 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?