Tom keeps all of his favorite marbles in a special leather bag. Right now, five red marbles, four blue marbles, and three yellow marbles are in the bag. 

1. If he randomly chooses one marble to give to a friend, what is the probability that it is blue?

   Hint (a):

   How many blue marbles are in the bag? How many marbles are there total?

   Answer (a):

   $\frac{4}{12}=\frac{1}{3}$

2. Tom does not really want to give away blue marbles and would like to change the probability that he chooses a blue marble to $\frac{1}{10}$ . How many marbles that are not blue could he add to the bag so that the probability of choosing a blue marble becomes $\frac{1}{10}$?

   Hint (b)

   If four blue marbles and eight non-blue marbles make a probability of $0.33$, how many non-blue marbles do you need to combine with blue marbles to achieve a probability of $0.1$?: