Ответ:

  1. \(2m-6m=-4m\);
  2. \(-3c+5c=2c\);
  3. \(7d-4d=3d\);
  4. \(10k-11k=-k\);
  5. \(-8p+9p=p\);
  6. \(-4n+3n=-n\);
  7. \(6x-10x=-4x\);
  8. \(-20y+30y=10y\);
  9. \(15e-14e=e\);
  10. \(t-2t=-t\);
  11. \(6b-8b+b=-b\);
  12. \(-3a-a-7a=-11a\);
  13. \(-5k-k+9k=3k\);
  14. \(x+x+x-4x=-x\);
  15. \(-c-c-c-c=-4c\).