= 7/13(13/7m- 26/49n) - 9/11(11/5m - 22/5n) - 4,5m + n =
= 7/4m - 2/7n -9\5m + 18/5n - 4,5m + n =
= (7/4m - 9/5m - 45/10m) - (2/7n + 18/5n + n) =
= ( 35/20m - 36/20m - 90/20m) - (10/35n + 126/35n + 35\35n) =
= - 91/20m - 171/35n = - 4 11/20m - 4 31/35n