Now apply this to an omnipotent being:
Creating a stone + Lifting a stone, these are 2 real things that an omnipotent being can obviously do. Now there is no problem until you simply ask that omnipotent being to create a stone he cannot lift, this is because trying to ask this being to do something outside the realm of reality. If they were truly omnipotent then the end result would be that he can create a stone he cannot lift, but at the same time can lift it. Thus negating the idea of an answer meaning a definite conclusion would be outside the possibility of this reality.
You're not asking him to do something outside the realm of reality. Creating something you cannot lift is perfectly possible. The only problem is because the being is omnipotent. This is a premise that can be challenged. A simple problem has been constructed, creating an object so heavy that one cannot lift. Anyone can create a building and be unable to lift it, why can't the omnipotent being?
Also, is there a definition for maths problem? When you give someone "1x5=5" and say 'solve this' how would they start? Rearranging, or 'solving' for 1+1=3 is from what we know impossible. Creating an object you cannot lift, is not impossible. It only seems possible for an omnipotent being to do so, as, the task contradicts his omnipotent nature. Suffice to say, an omnipotent being therefore cannot exist.
How about a scenario.
Bob asks Bill, 'hey bro, can you create something that you can't lift'?
Bill says, 'sure, lemme just put some weights in a box'.
* Bill tries but fails to move the box filled with weights.
Bill says, 'told you'.
Bob says to Bret, 'yo, can you do me a favor, I need someone strong'.
Bret says, 'sure, what do you need? I can do everything (I'm omnipotent).
Bob says, 'can you create something that you can't lift'?
Bret says, "this is outside the bounds of reality".
Bob says, 'no it's not, Bill just did it'.
This puerile scenario elucidates the point that creating something that you cannot lift is possible. I also hope the word 'create' doesn't get picked on semantically.