Hii Bhaskar.

I can help you here, there are a lot of Websites which offers Money on solving doubts of students. I personally know many of My friend working on Toppr.

Toppr is a good platform to solve doubts and Earn Money. Firs,t you need to create an account and then You will be assigned a task which you need to submit within five hours, once you submit it they review it and approve it. Approval is easy so dont worry about it , provided you are hardworking with Never Give up Attitude.

Here is the link to join

https://community.toppr.com/

Another such website is 

https://doubt.dubbtr.com/

Apart from this two, there are many sites not from India and difficult to Enter.

Chegg, tutor are some examples