@CHD2013 This one is a bit questionable. I do agree that on a few rare occasions a system of equations somewhat similar to this has shown up on the current SAT. But the hardest one I can remember was still a bit less involved than this one.
Most systems on the current SAT would allow you to perform a simple operation to get the answer quickly. In the rare case where elimination or substitution had to be used, the question would simply ask for x or y as opposed to the more complex expression asked for here.