Suppose that a\otimes b=ab-a-b. If (3\otimes x)\otimes3=11, then x= .
Suppose 3\otimes x=y, then y\otimes3=11\Rightarrow 3y-y-3=11\Rightarrow y=7.
3\otimes x=7\Rightarrow 3x-3-x=7\Rightarrow x=5.
