"Would you do that for me?"
Translation:¿Harías eso por mí?
I have seen another example on duolingo that uses "por" when it looks like a service on "behalf of" others. Los soldados han sufrido por su país. https://www.duolingo.com/comment/639488 "Para" is used for recipient of the action (like a gift) it does not seem to be right here but I'm not 100% sure why not.
after studying Spanish for something approaching half a century I am still confused by por and para, but recently did some research and found lots of interesting articles that helped. just search for "por vs. para.' and see what you get. the upshot is that (and I am still not and will never be totally sure) when you say do something "por mí" it is doing it " "in place of me"or "on my behalf." Doing something 'para mí' means as a gift to me. Both should be accepted in my opinion.