Ok, let me get this straight... you're talking about whole numbers, correct? If so, then 11+2=1 is mathematically impossible.
It maybe different if 11 or 2 is in a negative form
-11+2=
11-2=
But the first equals -9 and the other is 9. The only way for that to be possible is if you add a variable to it.
-11+2x w/ x = 6
so...
-11+2(6)=
-11+12=
1
So I presume that you want us to fill-in the gaps with variables in order to get the right answer?