I strongly suggest Khan Academy — https://www.khanacademy.org/math https://www.khanacademy.org/math Sal Khan is a great teacher --- I am doing now a uni cour

I strongly suggest Khan Academy — https://www.khanacademy.org/math https://www.khanacademy.org/math Sal Khan is a great teacher --- I am doing now a uni course (economy/informatics) and had to brush up on calculus and other math areas. Khan Academy helped me understand a lot of required concepts.