Решение задачи N3053 теория вероятностей

3053. In the urn 5 white and 4 black and 3 blue balls. In each trial, the ball is removed at random without returning it. Find the probability that a white ball appears at the first test (event A), at the second a black one is event B, and at the third one a blue event is C.

Detailed solution. Decorated in Microsoft Word 2003 (Quest decided to use the formula editor)