'x' g of molecular oxygen $\left(\mathrm{O}_{2}\right)$ is mixed with $200 \mathrm{~g}$ of neon (Ne). The total pressure of the non-reactive mixture of $\mathrm{O}_{2}$ and Ne in the cylinder is 25 bar. The partial pressure of Ne is 20 bar at the same temperature and volume. The value of 'x' is _________.

[Given: Molar mass of $\mathrm{O}_{2}=32 \mathrm{~g} \mathrm{~mol}^{-1}$.

Molar mass of $\mathrm{Ne}=20 \mathrm{~g} \mathrm{~mol}^{-1}$]