а) (3 7/30 − 1 5/12) : 18 1/6

\((3\frac{7}{30}-1\frac{5}{12}):18\frac{1}{6}=(\frac{97}{30}-\frac{17}{12}):\frac{109}{6}\)

\(=(\frac{194}{60}-\frac{85}{60})\cdot\frac{6}{109}=\frac{109}{60}\cdot\frac{6}{109}=\frac{1}{10}\)

Ответ: \(\frac{1}{10}\).