These are the Arihant Skills in Mathematics book series written by some renowned authors like Amit M. Agarwal sir and Dr. SK Goyal sir specifically for students preparing for JEE Main & Advanced. The one I am selling is of 2020-21 edition but there's little to nothing changed that are made in the newer additions. So students who are willing to purchase this series may buy these as they are significantly cheaper than the ones that are currently in the market as the newer editions. The price is negotiable.