$\mathrm{A}(\mathrm{g}) \rightleftharpoons 2 \mathrm{~B}(\mathrm{~g})+\mathrm{C}(\mathrm{g})$ For the given reaction, if the initial pressure is 450 mm Hg and the pressure at time t is 720 mm Hg at a constant temperature T and constant volume $V$. The fraction of $A(g)$ decomposed under these conditions is $x \times 10^{-1}$. The value of $x$ is $\_\_\_\_$ (nearest integer)