\[\boxed{\text{5.\ 39}}\]
\[\textbf{а)}\ x = 6:\]
\[\frac{1}{3} \cdot 6 = 2\]
\[3 \cdot 6 = 18\]
\[- \frac{1}{2} \cdot 6 = - 3\]
\[\frac{1}{2} \cdot 6 = 3\]
\[- \frac{1}{6} \cdot 6 = - 1\]
\[- 1 \cdot 6 = - 6\]
\[0 \cdot 6 = 0\]
\[2 \cdot 6 = 12\]
\[1 \cdot 6 = 6\]
\[- 6 \cdot 6 = - 36\]
\[\textbf{б)}\ x = \frac{1}{4}:\]
\[\frac{1}{2} + \frac{1}{4} = \frac{2}{4} + \frac{1}{4} = \frac{3}{4}\]
\[0 + \frac{1}{4} = \frac{1}{4}\]
\[- 2\frac{1}{4} + \frac{1}{4} = - 2\]
\[0,5 + \frac{1}{4} = \frac{1}{2} + \frac{1}{4} = \frac{3}{4}\]
\[\frac{1}{4} + \frac{1}{4} = \frac{2}{4} = \frac{1}{2}\]
\[- 1 + \frac{1}{4} = - \frac{3}{4}\]
\[- \frac{1}{2} + \frac{1}{4} = - \frac{2}{4} + \frac{1}{4} = - \frac{1}{4}\]
\[- \frac{3}{4} + \frac{1}{4} = - \frac{2}{4} = - \frac{1}{2}\]
\[\ - \frac{1}{2} + \frac{1}{4} = - \frac{2}{4} + \frac{1}{4} = - \frac{1}{4}\]