How is xp calculated during challenge such as answer bonus and match results

Answer 1

Challenge:
(XP + Bonus XP)
The XPs you gain/lose are unique to each match. Calculations take the opponents' levels into account. We use a modified version of the Elo rating system to calculate the points for each won/lost challenge. You can learn more about the Elo rating system here: 
https://en.wikipedia.org/wiki/Elo_rating_system

The best answer:
(upvote or downvote)+10 xp

Answer 2

https://www.sololearn.com/discuss/645720/?ref=app