\[\frac{5}{6} \cdot (12c + a) + \frac{2}{3} \cdot (3c - 2a) =\]
\[= 5 \cdot 2c + \ \frac{5}{6}a + 2c - \frac{4}{3}a =\]
\[= 10c + 2c + \frac{5}{6}a - \frac{8}{6}a =\]
\[= 12c - \frac{3}{6}a = 12c - \frac{1}{2}a = 12c - 0,5a.\]