Two known resistance of $\mathrm{R} \Omega$ and $2 \mathrm{R} \Omega$ and and one unknown resistance $\mathrm{X} \Omega$ are connected in a circuit as shown in the figure. If the equivalent resistance between points A and B in the circuit is $\mathrm{X} \Omega$, then the value of X is $\_\_\_\_$ $\Omega.\\$