Can anyone tell me how i am prepare for 90+% in class 12th cbse if I have 3 months
You should be dedicated and hard working to acheive your aim.
You can focus on important chapters which carries more weightage in the exam.
To score good marks it is very important that you have good hold on concepts. You should go through your text books throughly. Solve all the exercises which are given in your text book.
Solve previous year papers to understand the level of the questions. Sometimes, questions use to repeat in exam. So, it is good for your practice.
All the best for your exam!!