Bài giải:

$\begin{align}  & \frac{\frac{8}{12}:\left( \frac{7}{3}\times \frac{3}{9} \right)}{\left( 2\frac{5}{8}+1\frac{3}{4} \right):\frac{21}{24}}+\frac{3}{5}\times \frac{1}{2} \\  & =\frac{\frac{8}{12}:\frac{7}{9}}{\frac{35}{8}:\frac{21}{24}}+\frac{3}{10} \\ \end{align}$

$\begin{align}  & =\frac{\frac{6}{7}}{5}+\frac{3}{10} \\  & =\frac{6}{7}\times \frac{1}{5}+\frac{3}{10} \\ \end{align}$

$\begin{align}  & =\frac{6}{35}+\frac{3}{10} \\  & =\frac{33}{70} \\ \end{align}$