Question 204800
a) 
nP = n!
7P = 7!
=7*6*5*4*3*2
=5040
.
b)
 nCr = n!/[(n-r)!*r!] because arrangement is not important 
7C3 
= 7!/(7-3)!*3!
 =( 7*6*5*4!)/(4!*3!)
=(7*6*5)/(3*2)
=35 ways
.
Ed