Sir, I am currently studying in rajkot for prep of JEE and currently learning from reference books but could not solve some at once inspite of knowing formulas can you specify me a solution

it is a very common problem , mostly students face that, don't think about it you can easily solve these problems . don't just read chapter and formulas , try understand the concepts of topics. understanding concepts are very easy just take that concept try to relate with surrounding.
You should focus mainly on critical thinking and problem solving.
Here are my suggestions to improve it:-
◘ Learn basic and advanced mathematics necessary to increase your problem solving skills.
◘ Start from the easiest problem going to the hardest problem. Slowly you shall taste success.
◘ Focus why you are unable to solve that problem.
◘ Clear your opaque concepts.
◘ Question everything
Slowly, you will be able to think critically