So becuase the first card is a king and not replaced the remaining deck has 51 cards becuase a normal deck has 52 cards 4 of which are queends, therefore the probability of B given A, is the probability that a second card is a queen given the first card is a king which means there are 4 possible choices left for queens out of 51 cards becuase that king has been taken out and there is no longer 52 