Trigonometric Ratio And Identites

If \(\tan \left( {{\pi \over 9}} \right),x,\tan \left( {{{7\pi } \over {18}}} \right)\) are in arithmetic progression and \(\tan \left( {{\pi \over 9}} \right),y,\tan \left( {{{5\pi } \over {18}}} \right)\) are also in arithmetic progression, then \(|x - 2y|\) is equal to :