Hello Sumit Ashok Patel,

Yes, you can pursue both Mathematics as well as Biology in class 11th and 12th.

The rest part of your question is very unclear. Please do mention your query clearly, so that  we can solve it.

Rest I would suggest you to take wither of one subject as both Biology as well as Mathematics are time taking and you will completely be occupied in your studies and have no time for yourself. Rest is up to you.

ALL THE BEST