Ответ:

  1. \(14-x+9=15\) → \(23-x=15\) → \(x=8\).
  2. \(12-x+7=16\) → \(19-x=16\) → \(x=3\).
  3. \(18-x+3=12\) → \(21-x=12\) → \(x=9\).
  4. \(11-(13-x)=7\) → \(x-2=7\) → \(x=9\).
  5. \(15-(4+x)=6\) → \(11-x=6\) → \(x=5\).
  6. \(7+(14-x)=13\) → \(21-x=13\) → \(x=8\).

Ответ: 8; 3; 9; 9; 5; 8.