let's firstly convert the mixed fractions to improper fractions and then divide.
[tex]\stackrel{mixed}{1\frac{1}{3}}\implies \cfrac{1\cdot 3+1}{3}\implies \stackrel{improper}{\cfrac{4}{3}} \\\\[-0.35em] ~\dotfill\\\\ \cfrac{5}{8}\div 1\frac{1}{3}\implies \cfrac{5}{8}\div \cfrac{4}{3}\implies \cfrac{5}{8}\cdot \cfrac{3}{4}\implies \cfrac{15}{32}[/tex]
