Hi,

You can score 90 -100 in any subject. It all depends on how you consistently Preparing yourself. Pick the subjects you think you cant score. Spend more time on the chapters which you think you can't cope up with. Take help from your respective teachers where you facing difficulties. If studying in school, many students find difficulties in subjects like Mathematics and Science.

Mathematics chapters like Algebra, Vectors, Trigonometry, Analytical geometry are score able chapters.

Chemistry (organic) chapters like Ethers, Phenols, Basic Concepts are helpful to score good.

Physic Chapters like Solid State, Nuclear Chemistry  and Basic concepts.

This are some good chapters to score in JEE Mains. if you would have specified your education and chapters you'r talking about. I would definitely guide you more. Hope this help. Last but not the least advice, No matter which ever field of education you are into, Focus on the chapters/Subjects more which seems difficult to you, only then you can aim for 90-100 marks .

Thanks..