It is 5 [edit for clarification: the answer is choice number 5, the numerical answer is 2]. Each image represents a positive or negative number. Adding the first two items in a row gives you the third. Alternately, adding the last two items in a column gives you the first.
so it's 5, not 2. an outer and inner cancel each other out. then the remaining whether inside or outside are added to that same side.
Sorry, I was mixing up the numerical answer and the choice number. The answer is choice #5 in the list; the numerical answer is 2.
Just add the polarity of the loop counts (my solution, no idea if it's the right one).
I got 5: 1 inside + 3 outside = 2 outside. The other two rows look to be 4 inside + 1 outside = 3 inside and 3 outside + 2 outside = 5 outside.
Just addition with inside positive and outside negative (or vice-versa)