A sample of hydrated sodium phosphate has a mass of 190 g. Of this, 108 g is the mass of water of crystallization. What is the molar mass of the hydrated sodium phosphate ?
(Atomic mass of $\mathrm{Na}=23\mathrm{u},\mathrm{P}=31\mathrm{u},\mathrm{O}=16\mathrm{u},\mathrm{H}=1\mathrm{u}$)

Weight of compound is 190 gr.
Mass of water of crystallisation  is 108g
 weight of  ${\mathrm{Na}}_3{\mathrm{PO}}_4\text{ is }190-108=82\mathrm{g}$
1 mole of  ${\mathrm{Na}}_3{\mathrm{PO}}_4-1649$
So, 82g will be $0.5\mathrm{moles}\text{ of }{\mathrm{Na}}_3{\mathrm{PO}}_4$
$\text{ for }1\text{ mole }{\mathrm{Na}}_3{\mathrm{PO}}_4\text{, water of Crystallization is }2\times 108\mathrm{g}$
Finally 1 mole hydrated  ${\mathrm{Na}}_3{\mathrm{PO}}_4$ is heating
$\begin{array}{l}={\mathrm{Na}}_3{\mathrm{PO}}_4+\text{ Water of crystallization }\\ =164+216=380\end{array}$