Ответ:

  1. \(364+a+136=a+(364+136)=a+500\).
  2. \(67-(47+b)=(67-47)-b=20-b\).
  3. \(c-149-251=c-(149+251)=c-400\).
  4. \((n+251)-30=n+(251-30)=n+221\).
  5. \(98+(m-38)=(98-38)+m=60+m\).