Question

Mulder will read the files on ninenine unsolved cases from a list of fourteenfourteen. He does not care about the order in which he reads the files.

Answer 1

Since the order of the selection of files does not matter, this is the concept of combination not permutation.
therefore suppose we want the combination of 5 files that can be selected from 14. This will be given by:
14C5
=(14!)/(9!3!)
=2002
We therefore conclude that there are 2002 ways that 5 files can be selected from 14 files;