I've noticed, however, that my Polish students of English use "solution" in many situations where we would use "answer", which suggests to me that "rozwiązanie" has a rather broader usage than "solution" in English.
I don't think we can always pigeonhole translations on a 1:1 basis. In fact PWN/Oxford Wielki Słownik lists both "solution" and "answer" for "rozwiązanie".
Duolingo likes it literal, perhaps this should be included in the manual or something, so it doesn't have to be repeated over and over again. An entirely different matter is idiomatics, and idiomatic it would be to accept my answer: "Violence is no solution." I'm anything but a pro at English, but take this one for granted.