If I learn only theories in physics, chemistry , but not practice numerical so will I able to get above 70% in 12th with biology ? please tell
Board exams have a majority of questions from theory. So if you can do that you will get a 70% or above.
If you have learnt the theories you have a well number of time to practice problems so you can do that.
I hope my answer helps you. All the very best for your future endeavors!