$ \mathrm{T}_{\mathrm{r}+1}={ }^9 \mathrm{C}_{\mathrm{r}}\left(\mathrm{x}^{2 / 3}\right)^{9-\mathrm{r}}\left(\frac{\mathrm{x}^{-2 / 3}}{2}\right)^{\mathrm{r}} $

$ ={ }^9 \mathrm{C}_{\mathrm{r}}\left(\frac{1}{2}\right)^{\mathrm{r}}(\mathrm{r})^{\left(6-\frac{2 \mathrm{r}-2 \mathrm{r}}{3}\right)}$

for coefficient of $x^{2 / 3}$, put $6-\frac{2 r}{3}-\frac{2 r}{5}=\frac{2}{3}$

$\Rightarrow \mathrm{r}=5$

$\therefore$ Coefficient of $\mathrm{x}^{2 / 3}$ is $={ }^9 \mathrm{C}_3\left(\frac{1}{5}\right)^5$

For coefficient of $x^{-2 / 5}$, put $6-\frac{2 r}{3}-\frac{2 r}{5}=-\frac{2}{5}$

$\Rightarrow \mathrm{r}=6$

Coefficient of $\mathrm{x}^{-2 / 5}$ is ${ }^9 \mathrm{C}_6\left(\frac{1}{2}\right)^6$

$\text { Sum }={ }^9 \mathrm{C}_5\left(\frac{1}{2}\right)^5+{ }^9 \mathrm{C}_6\left(\frac{1}{2}\right)^6=\frac{21}{4}$