okay umm.. I am new at this website and I need help in math!

I was wondering if you guys cantell me if I am doing my work right?

here it is:

express each of the following as a product:

a.6!

my work:

720

6!=6x5x4x3x2x1

or on my calculator:

6 math-->prb-->4--> enter= 720

b. 7C 2

how would i do this one? thanks for your help in advance!