Bài giải:

$\begin{align}& \begin{array}{*{35}{l}}\text{ }~\text{ } & \frac{\left( 3\frac{3}{4}:\frac{1}{4}+2\frac{2}{5}\times 1\frac{1}{4} \right)-\left( \frac{7}{2}\times \frac{4}{5}-1\frac{1}{5}:\frac{3}{2} \right)}{\left( 1\frac{1}{2}+\frac{3}{4} \right)\times y}=64  \\\text{ }~\text{ } & \frac{\left( 15+3 \right)-\left( \frac{14}{5}-\frac{4}{5} \right)}{\frac{9}{4}\times y}=64  \\\end{array} \\& \frac{18-2}{\frac{9}{4}\times y}=64 \\& \frac{16}{\frac{9}{4}\times y}=64 \\\end{align}$

16 : $\frac{9}{4}\times y$ = 64

$\frac{9}{4}\times y$ = 16 : 64

$\frac{9}{4}\times y$= $\frac{1}{4}$

$y=\frac{1}{4}:\frac{9}{4}$

$y=\frac{1}{9}$