[tex]8\frac{5}{9}+3\frac{5}{6} +6\frac{4}{9} = (8 + 3 + 6)+(\frac{5}{9}+\frac{5}{6}+\frac{4}{9} )[/tex]
[tex]= 17 + (\frac{10}{18}+\frac{15}{18}+\frac{8}{18} )[/tex]
[tex]=17+\frac{33}{18}[/tex]
[tex]=17+1\frac{15}{18}[/tex]
[tex]=17+1\frac{5}{6}[/tex]
[tex]=18\frac{5}{6}[/tex]
Hence, [tex]8\frac{5}{9}+3\frac{5}{6} +6\frac{4}{9} = 18\frac{5}{6}[/tex]