Number of $\mathrm{B}-\mathrm{O}$ linkage in $\mathrm{Na}\left[{\mathrm{B}}_3{\mathrm{O}}_3(\mathrm{OH}{)}_{\uparrow }\right]=x$

Number of peroxy linkage in ${\mathrm{Na}}_2\left[{\mathrm{B}}_2{\mathrm{O}}_4(\mathrm{OH}{)}_4\right]=y$

Number of tetrahedral units of B in ${\mathrm{Na}}_2\left[{\mathrm{B}}_4{\mathrm{O}}_5(\mathrm{OH}{)}_4\right]=z$

Find the value of $x-(y+z)$

The structure of $\mathrm{Na}\left[{\mathrm{B}}_3{\mathrm{O}}_3(\mathrm{OH}{)}_{\uparrow }\right]$ can be given as,

Here, the number of $\mathrm{B}-\mathrm{O}$ linkage,

$\mathrm{x}=10$

The structure of ${\mathrm{Na}}_2\left[{\mathrm{B}}_2{\mathrm{O}}_4(\mathrm{OH}{)}_4\right]$ can be given as,

Here, the number of peroxy  linkage,

$\mathrm{y}=2$

The structure of ${\mathrm{Na}}_2\left[{\mathrm{B}}_4{\mathrm{O}}_5(\mathrm{OH}{)}_4\right]$ can be given as,

Here, the number of tetrahedral  linkage,

$\mathrm{z}=2$

Thus,

$$\begin{gathered} \mathrm{x}-(\mathrm{y}+\mathrm{z}) \\ =10-(2+2) \\ =6 \end{gathered}$$