90 percent of the posted questions, I cannot answer from my own experience, because I never ran into problems described in the question; my network always works, my printer, screen; no problems ever. Therefore, many times, looking through the questions, I am pretty sure I answered my last question around here. Nevertheless, every time after a while, some question pops up that I have the feeling "it is mine" to answer.
If you really want to answer questions (which you should only do if you like to), you will find out there is a "kind" of question or subject you are interested in and you are good at.
At the same time, there are lots of ways you can do useful things; edit posts, give useful comments review posts, vote on good (or bad) posts etc.
The quality is more important than the quantity in my opinion. An example: I asked this question a while ago. If you look into the profile of the person who answered the question, you can see he only posted... one answer. I consider the answer however to the very best answer to be found on this site :)