If the formula of Borax is ${\mathrm{Na}}_2 {\mathrm{B}}_4{\mathrm{O}}_x(\mathrm{OH}{)}_y·{\mathrm{zH}}_2\mathrm{O}$, then $\mathrm{x}+\mathrm{y}+\mathrm{z}= \_\_\_\_\_\_$

The crude name of borax is Tincal. It has the molecular formula ${\mathrm{Na}}_2{\mathrm{B}}_4{\mathrm{O}}_7.10{\mathrm{H}}_2\mathrm{O}$ and structural formula of borax is ${\mathrm{Na}}_2\left[ {\mathrm{B}}_4{\mathrm{O}}_5(\mathrm{OH}{)}_4\right].8{\mathrm{H}}_2\mathrm{O}$

Based on the structural formula, $\mathrm{x}=5, \mathrm{y}= 4 \mathrm{and} \mathrm{z}=8$

$(\mathrm{x} + \mathrm{y} + \mathrm{z}) = 5 + 4 + 8 = 17$