Susan's group of close friends are going to fifth grade in September. All are going to Belleview Elementary and their homerooms will be rooms 12, 14, or 16. All of her friends but 4 are going to room 12, all but 4 are going to room 14, and all but 4 are going to room 16. Not counting Susan, how many children are in her group of close friends?
Six.
If her number of friends is F, each room gets F -4 of them.
3(F-4) = F
2F = 12