Please note: this trick works for the SAT and the ACT, and for any other multiple choice math test as well! Also, as a lot of you have pointed out in the comments, this problem isn't particularly tough - and you're right! I'm just using this problem as an example. This trick is NOT better than just solving the math problem on your own if you know how. It IS a lot better than randomly guessing - so, if you're stuck on a problem, or if you're out of time, this trick will give you a far better than random chance of getting the right answer!