49
1+1=?

so let's start
1+1=1(1)+1(1) but 2-1=1 and 3-2=1
(2-1)(1)=(1)(3-2)
(2-1)(1)-(3-2)(1)=0
(1)((2-1)-(3-2))=0
so (1)(1-1)=0
(1)(0)=0
hence we know that 1+1=(2-1)+(3-2)

Ok after three hours of equations, finding the hidden numbers, and finding the invisible numbers, i have the answer.
huh