You have 9 different posters: 4 art posters, 2 movie posters, and 3 travel posters. In how many ways can you give the posters to three friends if the first friend does not receive any travel posters?
How many ways are there to give 9 posters to 2 friends.
Poster 1 can go to Aor B 2 ways
Poster 2 can go to A or B 2 ways
..
Poster 9 can go to A or B 2 ways
2^9 in total