Well, before you draw out the first sock, you had 60% chance of getting a white sock since six of the ten socks are white! (6/10)
So, if you were to not replace the first drawn white sock, your percentage goes to 55.5556%! This is because you now have 5/9 socks remaining in the drawer being white!
The probability that the first sock is white is 6/10 and that the second sock is white is 5/9, so the probability of choosing a pair of white socks is 30/90 = 1/3! Hope that helps.
