There are 23 total marbles (9 red, 7 white, and 7 blue). You want to select 4 marbles randomly without replacement. We want to know the probability of selecting 4 red marbles.
In this case, we have 3 different colors. By the formula (1 + 1 + 1)n = 3n, we can see how many possible outcomes of selecting 4 marbles randomly. Let n = 4.
There are 81 possible outcomes. We want to see which one has 4 red marbles. Only 1 possible outcome will give us that.
Therefore, P(4 red marbles) = 1/81 ≈ 0.01235
