OpenStax | Math
"Access. The Future of Education."
PhET Interactive Simulations
University of Colorado
"Free science and math simulations for teaching STEM topics, including physics, chemistry, biology, and math, from University of Colorado Boulder."
"The Textbook of the Future"
"At Desmos, our mission is to help every student learn math and love learning math. Explore and enjoy our collection of free digital math activities for you and your students."
Wolfram|Alpha: Computational Intelligence
"Compute expert-level answers using Wolfram’s breakthrough algorithms, knowledgebase and AI technology"
Math | cK-12
Below are a few awesome resources for learning about this subject.