Ответ:

  1. \(a-(a-(3a-5))=a-(-2a+5)=3a-5\).
  2. \(9x-((4-x)+5x)=9x-(4+4x)=5x-4\).
  3. \(6y-(4y-(3y-(y+2)))=6y-(4y-(2y-2))=6y-(2y+2)=4y-2\).
  4. \(8c-(3c-((d-c)-2d))=8c-(3c-(-c-d))=8c-(4c+d)=4c-d\).