Yes definitely you can get 75% above marks in your 12th boards exam.You can refer to your respective textbooks for preparation.Practice as much as you can.Firstly analyse your weak areas and make it strong.Clear all your doubts from your teachers or seniors.Solve previous years questions for practice and to enhance your skills.
Good luck!:)

You can definitely score 75+ if you start early and be consistent with dedicated efforts.

Remember, the early you prepartion is the more time you shall have for Competitive exams Like JEE, AIEEE, NATA , MHTCET.

By the moment, Class 12 exam starts you should have completed 50% sylkabus by mid year.

So you have ample time for practice and revision.

You can also solve previous year Board exam papers to gauge how much youbscore and how much more prepartion you require.