Xp calculation

Question

How xp is calculated for each challenge.. Like 2xp for some opponent and 25xp for another.. What's the calculation behind this?

Answer 1

Sololearn FAQ wrote ( https://www.sololearn.com/faq/#q13 ):

<< How are XPs calculated in the Challenges?

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 >>