6. Calculează:
A = (4 - 7)-(-11 + 19);
C= 27 - (+49) - (18 - 27) + (-28);
E = 27 - (+49)-(18-27)+(-28);
B=-(6-2) + 11 - 19;
D=1-(2-3) -(4-5)-(6-7) -(8-9)
F = 1-(2-3)-(4-5)-(6-7)-(8-9).

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