Please help with me find the area to read up on to solve this type of problem:
I have two bags. Bag one has 7 black marbles and 4 white marbles. Bag two has 4 black marbles and 5 white marbles. I take two marbles from bag one and put them in bag two (with a blindfold). If I take one marble out of bag two, what is the probability that it's white?
While I would like to know the answer, I would most like to know how to solve similar questions on my own.