let's firstly convert the mixed fraction to improper fraction.
[tex]\bf \stackrel{mixed}{5\frac{1}{5}}\implies \cfrac{5\cdot 5+1}{5}\implies \stackrel{improper}{\cfrac{26}{5}}\\\\\\ \stackrel{mixed}{1\frac{19}{20}}\implies \cfrac{1\cdot 20+19}{20}\implies \stackrel{improper}{\cfrac{39}{20}} \\\\[-0.35em] \rule{34em}{0.25pt}[/tex]
[tex]\bf \textit{area of a rectangle}\\\\ A=Lw~~ \begin{cases} L=length\\ w=width\\[-0.5em] \hrulefill\\ w=\frac{39}{20}\\[1em] A=\frac{26}{5} \end{cases}\implies \cfrac{26}{5}=L\cdot \cfrac{39}{20}\implies \cfrac{26}{5}= \cfrac{39L}{20} \\\\\\ 520=195L\implies \cfrac{520}{195}=L\implies \cfrac{8}{3}=L\implies 2\frac{2}{3}=L[/tex]
