>>>>It is possible. You have to divide the balls into 3 groups of four balls each. And then you should label each group A, B, and C. That gets you started.
>>>>
>>>
>>>I thought in this direction, but didn't come to a solution in case, the A and B don't weigh the same.
>>>
>>>>I've never heard of Great Ferma theorem. What is it?
>>>
>>>http://www.mbay.net/~cgd/flt/fltmain.htm
>>
>>You have to weigh a combination of balls so that the odd ball is narrowed to within three possible balls.
>>
>>Thanks for the link.
>
>Still could not make it. I'm trying to work at the same time, so this limits my mathematical capabilities (already quite limited)...

This theorem is, I hate to admit, a bit beyond my mathematical capabilities at this time. :)