[tex]E = 6 - (x+3) = 6-x-3=3-x\\\\G = 6 -(9-x) = 6-9+x = -3+x\\\\F = 6-(3-x) = 6-3+x = 3+x\\\\H = 3-(x+6) = 3-x-6 = -3-x[/tex]
[tex]A. \ E+F = 3-x+3+x=6\neq 0\\\\B. \ F+G = 3+x-3+x = 2x \neq 0\\\\C. \ G+H = -3+x -3-x = -6\neq 0\\\\\underline{D. \ E+F+G+H = 3-x+3+x-3+x-3-x = 0}[/tex]
[tex]\boxed{Odp. \ D.}[/tex]