\[3\frac{1}{6} + \left( - 2\frac{5}{9} \right) - \left( - 1\frac{7}{12} \right) =\]
\[= 3\frac{1^{\backslash 6}}{6} + 1\frac{7^{\backslash 3}}{12} - 2\frac{5^{\backslash 4}}{9} =\]
\[= 3\frac{6}{36} + 1\frac{21}{36} - 2\frac{20}{36} = 2\frac{7}{36}.\]