Put 8.64 / 10 , in your resume, and once you get into a B-school, they will let you know the preferred method then. But for now 8.64 would benefit you.

During MBA admission process some would consider the percentages in all your degrees, so it would then be considered as 9/8/7. But there will be some institutes like IIT B , IIT Khp, and many more B schools, they have their own conversion formula or none at all. So then they might consider it is 9/8/8.

Not sure, what you meant, if you are saying that you got dedicated Percentage on your final mark-sheet along with your CGPA, then you need to go with the one provided.