A bag contains 2 pink marbles, 2 black marbles, 2 red marbles, 2 orange marbles, and 4 green marbles. If 2 marbles are selected, what is the probability of picking 2 red marbles?

There are LaTeX: \displaystyle C(12,2)=66 to select 2 marbles. There are LaTeX: \displaystyle 1 ways to select 2 red from 2 red. This gives the probability LaTeX: \displaystyle \frac{1}{66}