"Fine, and you?"
Translation:Bien, ¿y tú?
I mean, technically it's correct, but I think duolingo means for you to answer "how are you" rather than "how is she/he".
This, though, is why I'd rather we practice responding in conversational manner rather than translating sentences back and forth. For example, in Korea, rather than "how are you" we ask, "are you well" so the answer is "yes" or people might even just nod and ask "are you well" back. So I've seen many people who learned English by translating just answer "how are you" by parroting the phrase back or even saying "yes". Learning the pragmatics of how the phrases are used would have helped, and in this case, would have helped to know whether we must say "estoy bien" or if we are talking about third person and must say "está bien".
But I guess that would be extra coding to account for all possible responses.