hello aspirant,

if you are talking about calculating PERCENTAGE , it is very easy task to do-

you need to check your results first of all and see what marks have you scored out of 300.

let suppose you have scored 'x' marks including all the three subjects out of 300 ,

then, you simply have to do-

(x/300)*100  , and in this way you can calculate your PERCENTAGE.

ALL THE BEST