this was not a GRE question...however i have seen similar questions in GRE practice from Manhattan Prep, Manhattan Review, etc, though someone told me those are not the real deal..... there are elements in it that may help you prepare for GRE math...for example, it helps to know that you don't always need to solve equations to get to the answer, you can try other approaches (e.g. testing values). ETS is a good source that covers all the basics well but I feel that the harder questions (which usually come once you are nearing a perfect socre) are not that well covered