Cycle Rule
If a 2 is placed in the green field the yellow field must be 2 also. But then there is no way to place 1 in the two areas.
Therefore the green field cannot be 2.
If a 2 is placed in the green field the yellow field must be 2 also. But then there is no way to place 1 in the two areas.
Therefore the green field cannot be 2.