we'll first off convert the mixed fractions to "improper", and then multiply.
[tex]\bf \stackrel{mixed}{5\frac{1}{3}}\implies \cfrac{5\cdot 3+1}{3}\implies \stackrel{improper}{\cfrac{16}{3}}
\\\\\\
\stackrel{mixed}{3\frac{3}{4}}\implies \cfrac{3\cdot 4+3}{4}\implies \stackrel{improper}{\cfrac{15}{4}}
\\\\\\
\cfrac{16}{3}\times \cfrac{15}{4}\implies \cfrac{15}{3}\times \cfrac{16}{4}\implies 5\times 4\implies 20[/tex]
