Answer:
If it's not 5396 which would be my first guess, maybe try every possibility?
Explanation:
So let's see here. There is a 5, a 3, a 9, and a 6.
5396
3965
9653
6539
or maybe try to do from decreasing order
9, 6 5 3
or maybe try to do from increasing order
4 5 6 9
or just play around with the numbers 5, 3, 9, and 6