How do SoloLearn earn?

Question

SoloLearn is a free app to download without any in-app purchases, ads nothing. So how do they earn or they are a team of professionals who do this as part-time...

Your answers and logic is appreciated!

Answer 1

https://www.sololearn.com/Discuss/334669/?ref=app

Answer 2

As @luka said in the link.. If you're really interested you can mail sololearn..
That and the article were the intention of my answer..

Answer 3

@Frost's answer contains the links to address your question. Please put some effort into digging. This question has been asked at least 10 times this month.

Answer 4

@Frost This don't gives my answer!