Решение задачи N2755 теория вероятностей

2755. There are 20 students in the group. 4 of them are excellent in math, 7 are good, and 9 are satisfactory. 5 students are randomly selected. What is the probability that among them there are 2 honors pupils and 3 horoshistas.

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