Buckyx, you're talking about the hexadecimal system, but it isn't meant here.
Just think about it, how easy would it be for a bot to solve a single math question.
That way the captcha of CookieRO is now, you can somewhat be sure that bots don't get to the solution, you may need a few tries yourself, but at least no bot can solve it.
As for CookieRO, the time wasted in that captcha is worth every second playing on the server.