Решение задачи N3562 теория вероятностей

3562. There are five balls in the urn with numbers from 1 to 5. At random, three balls are extracted without returning. Find the probability that the extracted balls will have numbers 1, 2, 3 regardless of the sequence in which they appeared.

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