Amira has \dfrac34 4 3 start fraction, 3, divided by, 4, end fraction of a bag of cat food. her cat eats \dfrac{1}{10} 10 1 start fraction, 1, divided by, 10, end fraction of a bag per week. how many weeks will the food last?

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?