\[\boxed{\mathbf{3.}\mathbf{281}}\]
\[\textbf{а)}\ 54b - 28 = 26\]
\[54b = 26 + 28\]
\[b = 54\ :54\]
\[b = 1.\]
\[\textbf{б)}\ 34s - 68 = 68\]
\[34s = 68 + 68\]
\[34s = 136\]
\[s = 136\ :34\]
\[s = 4.\]
\[\textbf{в)}\ 5905 - 27y = 316\]
\[27y = 5905 - 316\]
\[27y = 5589\]
\[y = 5589\ :27\]
\[y = 207.\]
\[\textbf{г)}\ 89n + 68 = 9057\]
\[89n = 9057 - 68\]
\[89n = 8989\]
\[n = 8989\ :89\]
\[n = 101.\ \]