Ranking system, how does it work?

Most games usually explain their mechanics, even if not in-game, somewhere easy to access. Like the civipedia on CIV games, or the items and champions, in LoL. Still, there is something I still don't understand, and I wish to know more about; the ranking system.

I posted a question yesterday regarding LP system, and it got deleted. I understand that maybe "help and support" was not in the right board to post it, but a notice, or any kind of feedback would have been nice. Still, I have the same questions. And I don't know where else but here to post it.

• How does LP system work?
• How does mastery system work?

I'm not talking about: "Earn points for your champion based on your team’s performance as well as your own contribution.". I am interested in the actual math behind the display. What numbers are there, or how it ranks the game. What defines the number of mastery points or LP i earn/lose after a game.

I just want to know how it works, no more no less. If anyone has any kind of data or opinion please, post.