Khan Academy is a free online education platform with thousands of lessons spanning various subjects. Subjects are subdivided by grade level and unit with tests and quizzes along the way.
How to use it:
1) Visit khanacademy.org
2) Use the drop-down menu to select your subject of choice, or use the search tool to search for a specific subject or unit.
3) Watch a video lesson or, if you prefer, read the video transcript instead.
4) If you want to learn a unit, watch the lessons for every chapter of the unit.
5) To test your knowledge, take a practice quiz or test.
6) Keep practicing until you feel comfortable with the material
Don't forget to use hints and read the solutions if you need to!
7) Check out your profile to track your progress and see the badges you've earned. You'll need to make an account to use this feature.
Good luck, and happy studying!