Okay I’ve been practicing my maths ever since I started joining Khan academy in 2015. Once I complete mastering all the basic k12 maths taught at school, I would like to take on higher mathematics like number theory, abstract algebra (including linear algebra), topology, real and complex analysis, combinatorics, and more because I would like to persue a career related to pure maths. Khan academy has help me a lot in my studies especially in math. It gave me deeper understanding of concepts and theories in math, but it would be great if you expand your subjects up to higher level maths that could help me. So it would really be handy for me if you include this subjects to your website. Also graph theory and group theory would be a great addition to the world of maths as well.