Hello Aspirant


Eligibility: Candidates must have completed 10+2 education with at least 50% marks aggregate in 5 subjects out of which 4 subjects Physics, Chemistry, Mathematics & English are mandatory subjects.

So, yes you're eligible for mathematics hons.

Admissions are mostly offered in the basis of your 12th class marks in most of the colleges / universities.
For more information:
https://www.careers360.com/courses/mathematics-course

But some universities like Jamia Milia Islamia conducts entrance exam, check out this link once:

https://university.careers360.com/colleges/list-of-bsc(hons)-in-mathematics-universities-in-india


Hope this helps!
All the best!