в) + =; 27 15 17 48 48 18 г) b + - = 14 3 20 23 23 23

в) $$\frac{27}{48} + \frac{15}{48} = a - \frac{17}{18}$$

$$\frac{27+15}{48} = a - \frac{17}{18}$$

$$\frac{42}{48} = a - \frac{17}{18}$$

$$a = \frac{42}{48} + \frac{17}{18} = \frac{7}{8} + \frac{17}{18}$$

Общий знаменатель: 72

$$a = \frac{7 \cdot 9 + 17 \cdot 4}{72} = \frac{63 + 68}{72} = \frac{131}{72}$$

Ответ: $$\frac{131}{72}$$

г) $$b + \frac{14}{23} - \frac{3}{23} = \frac{20}{23}$$

$$b + \frac{14-3}{23} = \frac{20}{23}$$

$$b + \frac{11}{23} = \frac{20}{23}$$

$$b = \frac{20}{23} - \frac{11}{23}$$

$$b = \frac{20-11}{23} = \frac{9}{23}$$

Ответ: $$\frac{9}{23}$$