SOLUTION:
After picking 1 black, 1 white, and 1 green sock without a replacement, what was left is 8 black, 9 white, 3 green and 2 pink, a total of 22.
If he picks another sock randomly, the probability that he will have a complete pair is calculated thus;
Pr (Black) + Pr (White) + Pr (Green)
[tex]\frac{8}{22}\text{ + }\frac{9}{22}\text{ + }\frac{3}{22}\text{ = }\frac{20}{22}\text{ = }\frac{10}{11}[/tex]The probability that he will have a complete pair is 10/11