Brain teaser

Bhav Bhuti Sharma (Towards Professionalism )   (823 Points)

20 July 2013  

My friend send this teaser to me and bets me i cant solve this in which he is right but not where written that i cannot take help wink

 

crack dis
5 - 4 = 23
8 - 1 = 63
6 -16 = 32
9 - 9 = 78
3 - 9 = 6
3 - 81 = ?
 
Anyone ?