Dr. B.R. Ambedkar Open University (BRAOU)

For M.Sc in mathematics, you need to have a Bachelor's degree in Mathematics.

You need to complete 10+2 with minimum 50% marks and also pass the eligibility test.

The first step you can take is to complete class 12. After you have cleared class 12th exams, you can then proceed to apply for a Bachelors course from a college based on the marks obtained in class 12th. You might have to appear for an entrance exam to secure admission in top colleges for your Bachelors of Arts.
Regards.

If you want to become a nutritionist, B.Sc in Nutrition should be the viable option for you.
How to become registered dietitian in India?
Educational qualifications required: B.Sc. in Home Science (Food and Nutrition) or B.Sc. in Nutrition and Dietetics or other relevant B.Sc. course. After B.Sc., one must also complete M.Sc. or PG Diploma in Clinical Nutrition or Food & Nutrition.
After completing relevant B.Sc. and M.Sc. courses, one must go through 6 months long internship stint at any one of the many hospitals recognized by the IDA OR possess 2 years work experience at any multidisciplinary hospital as a dietician. Regards.