These are tag questions, which can be a bit tricky for non-native speakers.
Often, we just say Yes or No. Sometimes we may repeat the tag and reverse it (They don't live here, do they? Yes, they do).
Important: Answer a tag question according to the truth of the situation. Your answer reflects the real facts, not (necessarily) the question.
In some languages, people answer a question like "Snow isn't black, is it?" with "Yes" (meaning "Yes, I agree with you"). This is the wrong answer in English!
A few examples:
- Snow is white, isn't it? Yes (it is). -> This answer can be really short, because you just confirm the truth that snow is indeed white.
- Snow isn't white, is it? Yes it is! -> Because you don't agree with the questioner, you have to make that clear by adding "it is" and stressing the last word.
Using the earlier example:
Snow isn't black, is it? No (it isn't). -> No can be sufficient here, which it wouldn't be if the questioner asked "Snow is black, isn't it?" Then you would have to make it very clear that the answer is no.
Hope this helps.