a) $$24 \cdot \frac{1}{48} + \frac{5}{14} = \frac{24}{48} + \frac{5}{14} = \frac{1}{2} + \frac{5}{14} = \frac{7}{14} + \frac{5}{14} = \frac{12}{14} = \frac{6}{7}$$.
б) $$(-9 + 5,7) \cdot 15 = (-3,3) \cdot 15 = -49,5$$.
Ответ: а) $$\frac{6}{7}$$, б) $$-49,5$$