Ответ:

[tex]\displaystyle6\frac{5}{9} +2\frac{7}{18} = 8 + \frac{5}{9} +\frac{7}{18} = 8 + \frac{5*2}{9*2} +\frac{7*1}{18*1} = 8 + \frac{10}{18} + \frac{7}{18} = 8 + \frac{7+10}{18} = 8+\frac{17}{18} =8\frac{17}{18}[/tex]