$\mathrm{A}\left(\mathrm{g}\right)\rightleftharpoons 2\mathrm{B}\left(\mathrm{g}\right)+\mathrm{C}\left(\mathrm{g}\right)$ 
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 voulume V. The fraction of A(g) decomposed under these conditions is $\mathrm{x}\times {10}^{-1}.$ The value of x is ___________ (nearest integer)