A group of students stood in three rows. The 1st row had 5a students. The 2nd row had 6a more students than the 1st row. The 3rd row had 9 less students than the 2nd row.
- Find the number of students in the 3rd row in terms of a. Give your answer in the simplest form.
- There were 24 students in the 3rd row. Find the value of a.