If an answer is not helpful, or directly addressing the question being asked you can use the "report as" link to bring it to a moderator's attention for review. I think what some people fail to keep in mind, is that just because something may seem like common sense, or that it should be easy enough to find the answer to on our own, doesn't mean that people aren't still allowed to ask such things. Not to mention that if someone truly doesn't know the answer - how else can they learn, but to ask.
Adding a bit of humor or sarcasm to one's on-topic answer can be fine, but when it's done specifically in a way that is rude or mocking the person asking, then it's not ok, and should be reported.
I admit to sometimes urging kids to read their homework instead of asking people for the answers. I do this because I want them to succeed, and you can't succeed if you don't actually learn your class material. Homework is a time for practice, and if you don't get it you should get help from your teacher before you get too far behind.