    Author: Rodney Shaghoulian
    Github: github.com/RodneyShag
HackerRank: hackerrank.com/RodneyShag


Answer: 2/3

After drawing the first marble, we are left with 2 red marbles and 4 blue marbles. 
Now we calculate the probability of drawing a blue marble as :

= (# of blue marbles) / (total # of marbles)
= 4 / (2 + 4)
= 2 / 3
