Greetings!

You can easily get 90+ with your planned strategy. But you must study the topic with whole concentration not just for the sake of completion. The course is vast and time is less, so try to give minimum eight hours a day to get good marks in each subject. Also, practice maths questions by writing in the notebook instead of reading them. Also, for chemistry and biology, it is a suggestion to read NCERT thoroughly as many conceptual question are asked from there only .

For more preparation tips for class12 board exam visit-

https://school.careers360.com/articles/cbse-class-12-preparation-tips

All the best!