At 10°C, the osmotic pressure of urea solution was formed to be 500 mm. The solution is diluted ‘x’ times and the temperature raised to 25°C when the osmotic prssure was noticed to be 105.3mm, then ‘x’ is

Osmotic pressure of Urea solution at 10°C
${\mathrm{\pi }}_1={\mathrm{iC}}_1{\mathrm{RT}}_1---\left(\mathrm{i}\right)$
Osmotic pressure of Urea solution at 25°C
${\mathrm{\pi }}_2={\mathrm{iC}}_2{\mathrm{RT}}_2---(\mathrm{ii})$

From equation 1 and 2
$$\begin{gathered} \frac{{\mathrm{\pi }}_1}{{\mathrm{\pi }}_2}=\frac{C_1\times 283}{C_2\times 298} \\ \frac{500}{105.3}=\frac{C_1}{C_2}\times \frac{283}{298} \\ {C}_1=5C_2 \end{gathered}$$

This means the solution was diluted to 5 times with respect to the urea concentration.