Ответ:

а)

\(1\frac{5}{17}=\frac{22}{17}\), \(2\frac{4}{11}=\frac{26}{11}\).

\(7-\frac{26}{11}=\frac{77}{11}-\frac{26}{11}=\frac{51}{11}\).

\(\frac{22}{17}\cdot\frac{51}{11}=\frac{2\cdot51}{17}=\frac{102}{17}=6\).

б)

\(42:12=3,5\), \(1,05:1,6=\frac{105}{160}=\frac{21}{32}=0,65625\).

\(3,5-0,65625=2,84375\).

Ответ: а) 6; б) 2,84375.