The total number of boron-oxygen bonds in borax is $\mathrm{\prime }\mathrm{x}\mathrm{\prime }$ and boron-oxygen-boron bonds are $\mathrm{\prime }\mathrm{y}\mathrm{\prime }$. Then the value of $\mathrm{x}-\mathrm{y}$ is:

Solution

$\mathrm{B}-\mathrm{O}$ bonds $=14$

$\mathrm{B}-\mathrm{O}-\mathrm{B}$ bonds $=5$

$\therefore \mathrm{x}-\mathrm{y}=14-5=9$

Hence, the correct answer is 9.