6) 1\frac{2}{7}x+4\frac{5}{7}y+2\frac{11}{14}x-\frac{11}{14}y.

6) Приведем подобные слагаемые:

$$1\frac{2}{7}x+4\frac{5}{7}y+2\frac{11}{14}x-\frac{11}{14}y = (1\frac{2}{7}+2\frac{11}{14})x + (4\frac{5}{7}-\frac{11}{14})y$$

$$= (1\frac{4}{14}+2\frac{11}{14})x + (4\frac{10}{14}-\frac{11}{14})y = 3\frac{15}{14}x + 3\frac{9}{14}y = 4\frac{1}{14}x + 3\frac{9}{14}y$$

Ответ: $$4\frac{1}{14}x + 3\frac{9}{14}y$$