You can do that in two ways :
(1) Use a logical approach as I mentioned in POINT (13) : You calculate "in how many different valid combinations, does a digit occur". From that knowledge, you can easily know its position.
(2) Brute-force ! Write a program in any language of your choice to brute-force all the valid combinations.
If you still have doubts, I can post a simple C++ Bruter here. Or I can explain POINT 13.