Thanks for the response.
Yes, I think it will work such answer, but still, I think that "more strong" should be added to correct answers as well. Bcs they give here the translation for "mai puternici" as "more powerful", but do not accept "more strong".
I am not complaining, the team have done a great job of adding Romanian to Duolingo, just think that it should be fixed :)
It's just that "more strong" isn't correct English. "Stronger" is the correct form.