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:
[tex]P(diamond)\text{ = }\frac{13}{52}[/tex](13 diamond cards in a total of 52). Then the probability to get a face card is:
[tex]P(facecard)\text{ = }\frac{12}{52}[/tex](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:
[tex]P(DiamondandFaceCard)\text{ = }\frac{3}{52}[/tex](We have only 3 cards in the deck that are diamond and face cards). Therefore, the probability will be:
[tex]\text{Probability = P(diamond) + P(facecard) - P(Diamond and Face Card)}[/tex][tex]\text{Probability = }\frac{13}{52}\text{ + }\frac{12}{52}\text{ - }\frac{3}{52}[/tex][tex]\text{Probability = }0.423[/tex]