There are 12 marbles in total. 4 of them are white.
The probability of getting a white marble on the first try is 4/12 or 1/3.
The probability of getting a second white marble in a row? Since you already pulled out a white marble on the first attempt, there are now 3 white marbles and 11 marbles in total. So the probability of getting a white marble at this point is 3/11.
Thus the probability of doing this back to back is 1/3 * 3/11 or 3/33 or 1/11.
The answer is B.
