The combined passing rule-

Suppose you have a paper which have Theory of 70 marks & practical/oral of 30 marks. Now in theory paper say you get 8 marks (which means you are failed in theory) & 29 marks in practical or oral then as per the combined rule you will be considered pass because out of 100 you are getting 37.

So you have to get above 35% combining both your theory & practical papers.

The best of Five rule:

Suppose you have 6 subjects say A,B,C,D, E, F. Now you got marks in A=90, B=56, C-70, D-82, E-99, F-38. Now in best of five you will take the subjects excluding the subject with least marks. In this case, the subject F have the least marks. So your best of five aggregate will be the sum of the marks obtained in A,B,C,D,E subjects.

I hope this answer helps. Wish you a great day!