I have two different answers:
The first answer is how many different sets there can be with regard to order. So like ABC, ACB, BAC are all different sets.
The second answer is without regard to order. So like ABC, ACB, BAC are just one set because it is all just one set of things arranged differently.
Maybe someone else can clarify which one is right.
P.S. I think it is probably looking for that first answer if I had to guess.
