A committee of five members is to be randomly selectedfrom a group of nine freshman and seven sophomores.Which expression represents the number of different committeesof three freshman and two sophomores that can be chosen?

The answer would be the product of the number of 3 freshman groups by 2 sophomores groups.
The number of 3 freshman groups is given by
[tex]C^9_3=\frac{9\times8\times7}{3\times2\times1}=84[/tex]The number of 2 sophomore groups is given by
[tex]C^7_2=\frac{7\times6}{2\times1}=21[/tex]Now, doing their product
[tex]21\times84=1764[/tex]We have 1764 different committees of three freshman and two sophomores.