I tried for maybe thirty seconds to solve it, but couldn't see anything obvious, so I decided to just truncate the fraction to see if it was close to anything I knew. From that it was clear the answer was root 2, but I still couldn't see how to solve it. Once I got into work though I had another look, and then (maybe because I knew what the answer was and could see that it was simple algebraically) I was able to come up with the above solution.