"Kiel fartas via edzo?"
Translation:How is your husband?
Mi skribis "how does your husband do", sed la angla ne estas mia gepatra lingvo...
The phrase "How do you do" is a little outdated and overly formal. Usually you shorten it to How are you or How are you doing.
"How does your husband do" is incorrect because "do" is transitive in this construction and the object is missing. To make it intransitive, use present continuous: "How is your husband doing".
I confused "fartas" with "is doing" and had to backtrack from "who is doing your husband"
That should be totally acceptable as long as you're visiting the late 18th century
Duolingo gives us sentences in isolation, without context. So we don't know which translations are appropriate. If we were translating a historical novel, "How fares your husband" might be not just a correct translation, but perhaps one actually required by the context.
In the absence of any context, it's safest to assume contemporary times and speakers with a high school or college education. That would make "How fares your husband" an unlikely translation.
If you mean about the question, then yes — you just have swapped the subject and the verb, in Esperanto that is permitted.