Probably of revealing 3-same, in a set of 9, composed of 3 sets of 3, by selecting 4. First - thanks for helping.  I'm admittedly a bit rusty in probability.  University is so far back!
In what looks like a traditional lotto game; I have a grid of 9 circles.  On this grid, there are 3 blue, red, and white circles -- each covered with that silvery scratch-off stuff that gets all over the place!
I fervently scratch 4 circles at random, hopeful to reveal 3 identical circles. 
What is the probability that I win?
Thanks for helping!
 A: Some hints:


*

*Calculate the number of ways that you can choose 4 positions from nine (where order doesn't matter).

*Count the number of ways you can win. If you have three the same, then one must be different. If you pick the three blues, then the other one is a red or a white. So that's six combinations (because you have your choice of three reds and three whites that can go in the fourth spot). How many more are there?

*Divide the number of winning combinations by the total number of possible combinations.

A: There are $\binom{9}{4}$ possible ways to pick $4$ circles in general, so this is the denominator of our probability. The numerator is the number of ways to pick a winning set of $4$ circles. 
There are $3$ ways to pick which color we win with. After picking those three circles with the same color, that leaves us with $6$ circles where the color won't match anything.
All in all, the probability is:
$$P = \frac{3 \cdot 6}{\binom{9}{4}} = \frac{1}{7}$$
A: Try writing out all the different possibilities and then finding the probability of each individual possibility
