A bag contains 3 red, 4 white, and 5 blue marbles. Jason begins removing marbles from the bag at random, one at a time. What is the maximum number of marbles he must remove to be sure that the bag consist at least 1 marble of each color?
What is the maximum number of marbles indicating to?
On
I would slightly rephrase the question.
What is the maximum number of marbles he may remove yet still be sure that the bag consist at least 1 marble of each colour?
So consider: How many marbles must be removed to become unsure that there is still at least one marble of each colour? (Without looking at the marbles removed.) The answer you require is one less than that.
This a puzzle/trick and not probability at all.
If he removes $3$ they might all red and he won't have $1$ of every color.
So the answer is $2$. If he removes only $2$ he can't run out of any color and if removes $3$ he might run out of red.
And that's all this question asks. Nothing more.