Two cards are drawn without replacement from a well-shuffled deck of 52 playing cards. what is the probability that the first card drawn is a spade and the second card drawn is not a spade

The probability that the first card drawn is a spade is 13/52. If a spade has been drawn on the first draw, there are 39 non-spade cards and a total of 51 cards remaining. Therefore the probability that the second card drawn is not a spade is 39/51.
The required probability is found as follows: