If there are 9 students to fill 9 desks, then this can be done in
9! = 362,880
ways. That is,
• the first seat can be filled by 1 of 9 students
• the second seat can be filled by 1 of the remaining 8 students left standing
• the third seat can be filled by 1 of the remaining 7 students
and so on until each of the seats are filled. Then you use the multiplication rule to get the total number of arrangements.
If Larry, Moe, and Curly are the names of 3 of the 9 students, then there are 6 students left to fill the remaining 6 desks, which can be done in
6! = 720
ways.
As for the first row of seats, Larry, Moe, and Curly and be rearranged in
3! = 6
ways. Then the total number of arrangements would be
3! • 6! = 4320