5 students are to be selected from 11 students.
(a) When 2 specified students are included, then remaining 3 students can be selected from (11 – 2) = 9 students. ∴ Number of ways of selecting 3 students from 9 students = 9C3
∴ Selection of students is done in 84 ways when 2 specified students are included.
(b) When 2 specified students are not included, then 5 students can be selected from the remaining (11 – 2) = 9 students.
∴ Number of ways of selecting 5 students from 9 students = 9C5
= 126
∴ Selection of students is done in 126 ways when 2 specified students are not included.