$\begin{array}{l}
a)\,\,y \times \dfrac{7}{9} = \dfrac{2}{3} + 2\dfrac{1}{2}\\
y \times \dfrac{7}{9} = \dfrac{2}{3} + \dfrac{5}{2}\\
y \times \dfrac{7}{9} = \dfrac{4}{6} + \dfrac{{15}}{6}\\
y \times \dfrac{7}{9} = \dfrac{{19}}{6}\\
y = \dfrac{{19}}{6}:\dfrac{7}{9}\\
y = \dfrac{{57}}{{14}}\\
b)\,\,\dfrac{5}{7} + y:\dfrac{9}{4} = \dfrac{4}{3}\\
y:\dfrac{9}{4} = \dfrac{4}{3} - \dfrac{5}{7}\\
y:\dfrac{9}{4} = \dfrac{{28}}{{21}} - \dfrac{{15}}{{21}}\\
y:\dfrac{9}{4} = \dfrac{{13}}{{21}}\\
y = \dfrac{{13}}{{21}} \times \dfrac{9}{4}\\
y = \dfrac{{39}}{{28}}
\end{array}$
