Решение задачи N3549 теория вероятностей Бернулли

3549. Conducted 20 independent tests, each of which consists in throwing three symmetric coins. Find the probability that:
a) at least in one trial from 20 3 emblems will appear;
b) in more than two trials 3 emblems will appear.

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