Math

http://www.coolmath.com/algebra

https://www.khanacademy.org/math

http://www.differencebetween.net/science/difference-between-algebra-and-calculus/

https://betterexplained.com/articles/a-gentle-introduction-to-learning-calculus/

https://math.wonderhowto.com/how-to/learn-calculus-20-minutes-295973/

https://www.mathsisfun.com/calculus/introduction.html

https://www.ixl.com/math/precalculus


http://www.bymath.com/studyguide/alg/alg_topics.html


https://www.khanacademy.org/math/algebra-basics

https://www.basic-mathematics.com/