how can i get 90% marks in 20 days???
Hoping OR considering that you are not a beginner asking this question but atleast someone who knows concepts a bit.. Then surely I can give you revising tricks... First of all toh get away from all the distractions and start studying sincerely from morning to night maximum hours possible. And try to byheart whole of chemistry, try to solve more and more maths as much as you can... And for physics, go for solving all the theorems and numericals again.
Best wishes. Thank you.