combinations and permutations problem

The question is: How many cards must be drawn (without replacement) from a standard deck of 52 to guarantee the following?

a) Two of the cards will be of the same suit

b) Three cards of the same suit

Since both questions are set up the same way I would appreciate help with either of those.

I really have trouble getting to a formula from a word problem. And, the only numbers I think I have to work with are 52, 13, and 2. I know that the answer is 5 as I've already read that you can draw 4 cards and the 5th card would be the 2nd card of one of the previously drawn suits. (because there are not 5 suits)

I guess my question is: are they looking for a formula? How would one set this up? Thank you for your consideration.