\[ -23 + 17 \cdot 6 = -23 + 102 = 79 \]
\[ 2 - \frac{5}{8} : \left(-\frac{9}{4}\right) = 2 - \left(-\frac{5}{8} \cdot \frac{4}{9}\right) = 2 + \frac{5 \cdot 4}{8 \cdot 9} = 2 + \frac{20}{72} = 2 + \frac{5}{18} = \frac{36}{18} + \frac{5}{18} = \frac{41}{18} = 2 \frac{5}{18} \]
Ответ: а) 79, б) 2 5/18