Figura 1 ( 5 + 7 ) - ( 5 + 1) = 6
Figura 2 ( 9 + 8 ) - ( 3 + 4 ) = 10
Figura 3 ( 11 + 9 ) - ( 7 + 4 ) = 9
Figura 4 ( 13 + 11 ) - ( 10 + 12 ) = 2
R : X = 2
