\[7\frac{3^{\backslash 3}}{8} - 3\frac{5^{\backslash 4}}{6} = 7\frac{9}{24} - 3\frac{20}{24} =\]
\[= 6\frac{33}{24} - 3\frac{20}{24} = 3\frac{33 - 20}{24} = 3\frac{13}{24}\]