Question

permutations of the word September?

Answer 1

factorial 9 / factorial 3

Answer 2

So there are 9 letters in September. We initially consider them distinct.
that gives us 9 obvious to permute, so we use the normal 9! for the number of permutations.
However 3 of the objects (the e's) are indistinguishable, so we recognize that there's 3! permutations for the "distinct e's" that we have to divide out for all the permutations.
It's the basic principle of counting so

Answer 3

Thanks to you both :)