Why don't you give us some of your thoughts on these. They're not that bad.
How about 2a and 2b?. How many ways are there to choose 3 out of 14?.
If there must be at least one of each gender and 3 are to be chosen, what are the cases?.
3c was answered by plato. For 3d, think about it a little. There are 8 letters, 3 must be A's, 3 must be B's, that means the other two are C's.