Ответ:

а)

\(7\frac{1}{9}-6\frac{2}{15}+\frac{2}{9}=\frac{64}{9}-\frac{92}{15}+\frac{2}{9}=\frac{54}{45}=\frac{6}{5}=1,2\).

\(1,2:0,8+1,2=1,5+1,2=2,7\).

б)

\(8\frac{7}{12}-2\frac{17}{36}=\frac{103}{12}-\frac{89}{36}=\frac{220}{36}=\frac{55}{9}\).

\(\frac{55}{9}\cdot2,7=\frac{55}{9}\cdot\frac{27}{10}=\frac{33}{2}\).

\(4\frac{1}{3}:0,65=\frac{13}{3}:\frac{13}{20}=\frac{20}{3}\).

\(\frac{33}{2}-\frac{20}{3}=\frac{99-40}{6}=\frac{59}{6}=9\frac{5}{6}\).

Ответ: а) 2,7; б) \(9\frac{5}{6}\).