Dear Swati,

If you want to pursue the graduation degree in science with maths then you can give many entrance exam which are as follows.

1. If you have completed your 12th with good marks then you can take direct admission in Delhi University just by filling the application form. Remember that the cutoff of Delhi University is little bit high especially for science section, you need minimum 98% for any campus.
2. JNU form is released and you can apply here also, you need to give the entrance exam here, they will  not take admission in the merit based.
3. Aligarh muslim university last date is passed to apply online so here you missed that.
4. BHU and AU still has to announce the application form date, so it will be big opportunity here for you.
5. And some other entrance exams like JMI, Jadavpur University, and some other.

You just need to apply the application form for where you want to take admission, then you need to clear the exam, participate in counselling then they will alot you the campus according to your score.

Good Luck :)