Решение задачи N3357 теория вероятностей

3357. The student knows 18 of the 30 questions in the program. Find the probability that of the three questions proposed to him by the examiner the student knows: a) at least two questions; b) at least one question; c) none of the questions.

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