Решение задачи N2837 теория вероятностей

2837. In the group of 30 students in the control work received: 6 students rated excellent, 10 students rated good, 9 students rated satisfactory. What is the likelihood that all three students brought to the board have unsatisfactory marks for the test?

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