In one deck we have Spades, Clubs, Hearts, and Diamonds. Each one has 13 cards and 3 face cards. So the let's do this step by step. The probability to get a diamond card is:
(13 diamond cards in a total of 52). Then the probability to get a face card is:
(12 face cards in a total of 52). We have to sum these probabilities but also we have to subtract the possibilities that include a card that is a face card and diamond (because if we don't do that we are going to count these cards two times). This probability is:
(We have only 3 cards in the deck that are diamond and face cards). Therefore, the probability will be: