Question 918991
In this problem you will either have a permutation or a combination.  But how do you tell?   

With a permutation, the order or how the items are arranged matters greatly.
With a combination, the order doesn't matter at all.  

The example above talks about a problem where it doesn't matter what
order the players are in.  We can have the 5 player teams in any order. 
Therefore its a combination.  

The formula for a combination is  nCr = n!/(n-r)!  

where n =  total number of items
r =  number of items of subgroup 

examples of n! (separate from the problem) 
4! = 4*3*2*1
9! = 9*8*7*6*5*4*3*2*1
______________________________

 nCr = n!/r!(n-r)!

n = 7,  r =5  

7C5 = 7!/5!(7-5)!  = 7*6*5*4*3*2*1/[(5*4*3*2*1)(2*1)]
7C5 =  7*6/2
    = 21