Question 4083
Since n=5 and r=3 (five people taken three at a time), then the equation is as follows

Use the following formula for combinations nCx=(n,x)=n!/x!(n-x)
Looks confusion doesn't it.  

n=5
x=3


Now solve

5 x 4 x 3 x 2 x 1
_________________
3 x 2 x 1 x 2 x 1

You can cross out or multiply and divide. 

120/12 = 10