One card is drawn at random from a pack of 52 cards. What is the probability that the card drawn is either a red card or a king?

Clearly n(S) = 52. There are 26 red cards (including 2 kings ) and there are 2 more kings.
Let (E) be the event of getting either a red card or a king .
Then, n(E) = 28
∴ P(E) = n(E) / n(S) = 28/52 = 7/13