Russel will own 8 black with different colored stripe ties.
If he has a total of 12 ties, and 3 ties per set, there will be 4 groups of 3 because 3 times 4 equals 12
If 2 out of 3 ties are black with different colored stripes, and there are 4 sets, we would multiply 2 and 4, which will give you 8
Hope my explanation is good enough!