Hey Divya!

If you Google libgen, then you will get a bunch of sites from where you can get books online for free.

For Real Analysis:

1. You can refer to Bartley and Sherbet or Rudin. There is a book by Kumaresan and Ajith Kumar as well.
2. There are three volumes of problem book on Real Analysis by Kaczror and Nowak.

For linear Algebra:

1. Linear algebra done right by Axler

2. The book by Friedberg and two others is also pretty good

3. Algebra by Artin is nice as well.

For Modern Algebra:

1. Abstract Algebra by Dummit and Foote

2. The book by Gallian can be used as well.

All the best!