reserve w, w1, w2 for Element of ExtREAL;
reserve c, c1, c2 for Complex;
reserve A, B, C, D for complex-membered set;
reserve F, G, H, I for ext-real-membered set;
reserve a, b, s, t, z for Complex;
reserve f, g, h, i, j for ExtReal;
reserve r for Real;
reserve e for set;

theorem
  A -- (B /\ C) c= (A--B) /\ (A--C)
proof
  A -- (B /\ C) = A++((--B)/\--C) by Th16;
  hence thesis by Th49;
end;
