<p>Out of a workbook. The problem was pretty self-explanatory after the little lesson, but I've never seen this in any official materials. here goes:

4. A bag contains 8 white marbles, 8 blue marbles, 7 red marbles, and 6 yellow marbles. What is the least number of marbles that can be drawn from the bag, so that 3 of the same color marbles will be drawn?</p>

<p>(A) 6

(B) 9

(C) 12

(D) 13

(E) 15</p>

<p>The right answer is (B).</p>