If you draw one card from a deck of cards, what is the probability that it is a heart or a diamond?
In a standard deck of cards (no jokers) it is
Whenever you see EITHER... OR in a question like this you may ADD the probabilities.
13 hearts + 13 diamonds = 26 out of 52 cards.
So the probability for "success"
(if you have a deck including 2 jokers it would be slightly less: