\[4 \bullet (4c - 3) - (10c + 8) =\]
\[= 16c - 12 - 10c - 8 = 6c - 20\]
\[c = \frac{5}{6}:\ \ \ \ \ \ \ \ \]
\[6 \cdot \frac{5}{6} - 20 = 5 - 20 = - 15.\]
\[Ответ: - 15.\]