greetings ajay,

you admission in delhi university will depend upon you marks in class 12th.

following is the course for bsc mathematics hons:

http://www.du.ac.in/du/uploads/Syllabus_2015/B.Sc.%20Hons.%20Mathematics.pdf

fee structure of DU colleges is more or less the same. tuition fee in from 10,000 to 20,000 rupees anually.

following are the best colleges:

• st stephens
• hindu college
• kirori mal college
• ramjas college
• hansraj college
• sri venkateshwara college

pls refer to the previous year cut-off:

http://www.du.ac.in/cut-off.html

hope this helps.

good luck.