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There are 3 ways to sit Mrs. Brown in the first row.View attachment 59575
(ii) & (iii) part
Once Mrs. Brown is placed in the first row, there are 10 ways in which Mrs. Lin sits behind a student. There're 5 possible students behind which Mrs. Lin sit. So the no. of ways in which Mrs. Lin sits behind a student are 10 * 5.
Now there're 9 Passengers left to be seated in 11 seats. The no. of ways of seating 9 passenger in 11 seats are : 11P9.
So the total ways for seating passengers in this way are: 3* 10 * 5 * 11P9
The total no. of ways for seating passengers with no restrictions are: 14P12
The probability is : (3* 10 * 5 * 11P9) / 14P12 = 0.06868 ~ 0.0687 (3sf) Ans.