Titration calculations

A student dissolves 12.6 g of hydrated sodium carbonate, $\text{Na}_2\text{CO}_3\cdot x\text{H}_2\text{O}$, in water and makes up the solution to 250 cm³. Titration with 0.150 mol/dm³ HCl shows that 23.4 cm³ of acid is needed to neutralise 25.0 cm³ of the carbonate solution.

$\text{Na}_2\text{CO}_3 + 2\text{HCl} \rightarrow 2\text{NaCl} + \text{CO}_2 + \text{H}_2\text{O}$

What is the value of $x$? ($M_r(\text{Na}_2\text{CO}_3)=106,\ M_r(\text{H}_2\text{O})=18$)