Mila has a loyalty card good for a discount at her local grocery store. The item she wants to buy is priced at $10,before discount and tax. After the discount, and before
tax, the price is $8.40. Find the percent discount.

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?