Ответ:

а)

\(2\frac{2}{3}=\frac{8}{3}\), \(1\frac{7}{9}=\frac{16}{9}\).

\(\frac{8}{3}:\frac{16}{9}=\frac{8}{3}\cdot\frac{9}{16}=\frac{3}{2}\).

\(\frac{43}{63}-\frac{23}{36}=\frac{172}{252}-\frac{161}{252}=\frac{11}{252}\).

\(\frac{55}{84}:\frac{11}{252}=\frac{55}{84}\cdot\frac{252}{11}=15\).

\(\frac{3}{2}+15=\frac{33}{2}=16\frac{1}{2}\).

б)

\(5\frac{5}{7}=\frac{40}{7}\), \(1\frac{8}{13}=\frac{21}{13}\).

\(\frac{40}{7}:\frac{8}{21}=\frac{40}{7}\cdot\frac{21}{8}=15\).

\(\frac{43}{56}-\frac{11}{24}=\frac{129}{168}-\frac{77}{168}=\frac{13}{42}\).

\(\frac{21}{13}\cdot\frac{13}{42}=\frac{1}{2}\).

\(15+\frac{1}{2}=15\frac{1}{2}\).

Ответ: а) \(16\frac{1}{2}\); б) \(15\frac{1}{2}\).