It really depends on the users voting on the definition of "duplicate," which is why this is a democratic process.
By definition, however, it means that the general question you've asked have already been asked and answered, and the answer for the given question should work for you.
If the duplicate target does not answer your question, you may edit your question to make it sufficiently different, or point out why the duplicate target does not answer your question. Optionally, you may appeal your case on meta, where the community at large (or one of our gods moderators) will decide on your case.