Two known resistances of R Ω and 2 R Ω and one unknown resistance X Ω are connected in a circuit as shown in the figure. If the equivalent resistance…

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