In descending order, we arrange the numbers in decreasing order.
So, on comparing these numbers we see that,
All the numbers have 6 in their ten thousand's place and 8 in their thousand's place.
So, on comparing the digits at hundred's place, we have
7 > 6 > 5 > 3
⇒ 68,785 > 68,689 > 68,589 > 68,375