Using , you seem to be working with permutations.
. . Sorry, I don't understand your answer.
There are: . possible samples.A drawer contains 5 different and distinguishable pairs of socks (total of 10).
If a person randomly selects four socks, what is the probability that
there is no matching pair in the sample?
Suppose the pairs of socks are of five different colors.
To have no matching pairs, we must have four socks of different colors.
There are: . choices for the four colors.
Then we must select one sock from each of those pairs.
. . There are: . ways.
Hence, there are: . ways to get four socks of different colors.