Answer :
Combine the like terms.
[tex]\sf-abc+7abc-3bc-8abc[/tex]
[tex]\sf-abc+7abc-8abc=-2abc[/tex]
So we have:
[tex]\boxed{\sf-2abc-3bc}[/tex]
[tex]\sf-abc+7abc-3bc-8abc[/tex]
[tex]\sf-abc+7abc-8abc=-2abc[/tex]
So we have:
[tex]\boxed{\sf-2abc-3bc}[/tex]