I know these should be relatively simple but combinatorics has always been my Achilles heel. If you could explain these to me that would be awesome? I am really struggling to wrap my head around how you do these.

How many 5 card hands have two or more kings? How many 5 card hands contain the ace of spades, ace of clubs or both? In how many ways can 3n students be broken up into groups of 3? How many directed graphs are there with n vertices (self loops

ok)? How many tournament graphs are there with n vertices? How many acyclic tournament graphs are there with n vertices?

Thanks!