\[\frac{1}{6}\ \ и\ - \frac{1}{2}:\]
\[\frac{1}{6} + \left( - \frac{1}{2} \right) = - b\]
\[\ \frac{1}{6} - \frac{3}{6} = - b -\]
\[\frac{2}{6} = - b\]
\[b = \frac{1}{3}.\]
\[\frac{1}{6} \cdot \left( - \frac{1}{2} \right) = c\ \ \]
\[- \frac{1}{12} = c\]
\[c = - \frac{1}{12}.\]