# Math Help - Combinations of a Set

1. ## Combinations of a Set

Hello Everyone!

I just want to check something here...

Say we have a set $E = {a_1, a_2, \cdots a_n}.$

And we want to get all the subsets of size $k$ and of size $p$ call this set of subsets $S$

So is $|S| = C_n ^k + C_n ^p$??