"what is going to be where the dots are?"is that the dots indicate that the pattern continues but some terms are not shown.
So, for example, the first component is n/k as shown, the next is (n-1)/(k-1) as shown, the next (not shown) is (n-2)/(k-2), then it's (n-3)/(k-3). This continues until we get to the final component which is as shown
Replace n and k by numbers such as 6 and 4 to see what's happening. If n=6 and k = 4 the calculation will be:
(6/4) x (5/3) x (4/2) x (3/1)