Khan Academy - Khan Academy offers online tools to help students learn about a variety of important school subjects. Tools include videos, practice exercises, and materials for instructors. Read more about Khan Academy.
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edX - Best Courses. Top Institutions. Learn anytime, anywhere.
Learnetto - Learnetto is a place to learn how to make web and mobile apps.
Coursera - Build skills with courses, certificates, and degrees online from world-class universities and companies
Math42 - Formula calculator for IOS