The probability is given as No of favourable outcomes over total number of events. Now, the no of clubs in a deck of cards is 13 and similarly, the number of jacks in a deck of cards is 13. Then, the probability that a card picked at random from a 52-card deck of playing cards is a club or a jack = 13+13/52 = 26/52 = 1/2 = 50%
