Let us consider an arrangement where the teenagers sit together.
The rest of the seven persons who are not teenagers can be arranged in 7! ways
The three teenagers can themselves sit in 3! ways.
therefore the total number of arrangements are
7!X3!
Let us consider an arrangement where the teenagers sit together.
The rest of the seven persons who are not teenagers can be arranged in 7! ways
The three teenagers can themselves sit in 3! ways.
therefore the total number of arrangements are
7!X3!