What answer would that be?
The most likely interpretation I can think of for this question is that it is asking somebody to provide context for an answer that they have just mentioned. As in:
Fred: "I have the answer!"
Mary: "What answer would that be?"
Fred: "Oh, I just figured out [something]."
In my example, at first Mary doesn't know what Fred is talking about because he has just blurted out that he has "the answer" without explaining what question it answers, so Mary asks him what answer he is talking about.
(There may be other interpretations. If you could quote the sentences that appeared before that one then perhaps I could help further.)
He is a farmer but it wouldn't mean that he's laborious. (why "wouldn't" has been used here and what's its meaning here?)
When describing a person, laborious means "diligent and hard-working". Farmers are often thought of as being very hard-working, getting up early and spending the day doing physically demanding tasks out in the fields. Your sentence seems to be saying that although "he" is a farmer, that doesn't necessarily mean that he actually does work hard.
It's kind of an odd way to phrase it though. I would use that rather than it and doesn't rather than wouldn't: "He is a farmer, but that doesn't mean that he's laborious."
In general, the form he is X, but that doesn't mean he is Y is saying that although people who are X are often Y too, they don't have to be.