Explanation:
There are 13 clubs in the deck of 52 cards. That makes the probability of the first card being a club 13/52, which reduces to 1/4.
For the second card, there are 12 clubs in the 51 that remain, so the probability it's a club is 12/51, or 4/17.
There are now 11 clubs in the remaining 50, so the probability the third card is a club is 11/50.
Finally, you have 10 clubs out of 49 cards, making the probability that the 4th card is a club is 10/49.
To get the probability of this whole scenario, just multiply the four fractions (and simplify).