Hello,It totally depends on you and your level of preparation for class 12th board exams.No book or person can assure you that you will get that much marks...It's only up to you to score the board exams.I will suggest only to focus on textbooks for your preparation as questions are based on your textbooks.Solve previous years questions so that this will help you in determining the pattern of questions asked in 12th board exams.
Go through textbooks and clear all your doubts from your teacher or coaching institute.Follow a proper timetable and give equal time to each subject.
Good luck.