Ответ:

  1. \(6a+2a-3a=5a\).
  2. \(12b-7b+4=5b+4\).
  3. \(8y-5+y+2=9y-3\).
  4. \(-4x+9x-2x=3x\).
  5. \(7m-3+2-5m=2m-1\).
  6. \(-6c+4c+8-1=-2c+7\).