Fraction of Gas Decomposed Calculation

A(g)⇌2B(g)+C(g)
For the given reaction, if the initial pressure is 450‌mmHg and the pressure at time t is 720‌mmHg at a constant temperature T and constant volume V. The fraction of A(g) decomposed under these conditions is x×10−1. The value of x is _________ (nearest integer)