out of 52 cards 4 are jacks so there is a 4/52 chance the chosen card is a jack
then since the card is put back there are still 4 jacks so there is still a 4/52 chance the second card is a jack
to find the probablility for both cards we need to multiply
4 4
--- × --- = 0.0059
52 52
the probability that both cards chosen is a jack is 0.0059
I hope I've helped!
