a) \(461+\left(x-45\right)=387\)
\(x-45=387-461\)
\(x-45=-74\)
\(x=-74+45\)
\(x=-29\)
b) \(11-\left(-53+x\right)=97\)
\(11+\left(53-x\right)=97\)
\(53-x=97-11\)
\(53-x=86\)
\(x=53-86\)
\(x=-33\)
c) \(-\left(x+84\right)+213=-16\)
\(-\left(x+84\right)=-16-213\)
\(-\left(x+84\right)=-229\)
\(x+84=229\)
\(x=229-84\)
\(x=145\)