x = 64 IS the answer. But, the remaining question remains unsolved. You see, my teacher hates it when we don't have the SOLUTION, so I can't just say trial and error. That's I.A. she even gave that problem without even teaching us how to solve anything like that, lol. So yeah.
University!! <3 I wanna go abroad, haha. :3 But, 2 more years. :P you'll miss your P.E. teacher? I won't. xD