Question 22203
I'm going to assume your question was "How many committees of four students 
can be formed from a class of fifteen students?".

Since the committee is a group of people you want to count the "number of combinations of size four in a group of size fifteen".

The combination answer if 15C4 which is 15!/[(15-4)! (4)!]
This is the same as [15*14*13*12]/[1*2*3*4] which the same 
as 1365.

Good luck.
Cheers,
Stan H.