Free online lectures on topics in Micro and Math by Amit Goyal.
For access to the complete courses with exercises (available for free), you can register at
http://learn.econschool.in/ [for Short Courses]
http://class.econschool.in/courses/EconSchoolX/ES021/2020-21/about [for Full Course - all in one]
Modeling consumer behavior
Graphical approach to finding demand
Substitution and income effect