2 cards are drawn from a deck of 52 playing cards at random without replacement.
(a) Find the probability that both cards drawn are of the same unit.
(b) Find the probability that both cards drawn are face cards given that they are of the same unit.
2. Relevant equations
3. The attempt at a solution
I have no problem with the part (a) but part (b) makes me confused.
Do I have to use conditional probability to work out the solution of part (b)?
If that's the case, how to determine the event involved? In other words, how to do?