\[3\frac{5^{\backslash 4}}{6} - 5\frac{3^{\backslash 3}}{8} = 3\frac{20}{24} - 5\frac{9}{24} =\]
\[= - \left( 4\frac{33}{24} - 3\frac{20}{24} \right) = - 1\frac{13}{24}.\]