There are 20 balls in a jar. You take out 2 blue balls without putting them back inside, and now the probability of pulling out a blue ball is 1/5. How many blue balls were there in the beginning?  Choose the correct choice from the following.
A) 12.  B) 9.  C) 8.  D) 7.  E) 6.
12 = 3 blue balls + 18 / 2   12.nswer: 12.
<result>A</result>
There are 20 balls in a jar. You take out 2 blue balls without putting them back inside, and now the probability of pulling out a blue ball is 1/5. How many blue balls were there in the beginning?