\[\boxed{\text{5.544.}}\]
\[\textbf{а)}\ (z - 6) \cdot \frac{3}{7} = 3\]
\[z - 6 = 3\ :\frac{3}{7}\]
\[z - 6 = 3 \cdot \frac{7}{3}\]
\[z = 7 + 6\]
\[z = 13\]
\[Ответ:z = 13.\]
\[\textbf{б)}\ \frac{1}{4}y - \frac{1}{4} = \frac{1}{4}\]
\[\frac{1}{4}y = \frac{1}{4} + \frac{1}{4}\]
\[\frac{1}{4}y = \frac{2}{4}\]
\[y = \frac{2}{4}\ :\frac{1}{4} = \frac{2}{4} \cdot 4\]
\[y = 2.\]
\[Ответ:y = 2.\]