Решим данные примеры.
а) $$0,5 + \frac{1}{3}$$
$$0,5 = \frac{1}{2}$$
$$\frac{1}{2} + \frac{1}{3} = \frac{3}{6} + \frac{2}{6} = \frac{3+2}{6} = \frac{5}{6}$$
б) $$\frac{5}{6} + 0,75$$
$$0,75 = \frac{3}{4}$$
$$\frac{5}{6} + \frac{3}{4} = \frac{10}{12} + \frac{9}{12} = \frac{10+9}{12} = \frac{19}{12} = 1\frac{7}{12}$$
в) $$\frac{19}{21} - \frac{11}{15}$$
$$\frac{19}{21} - \frac{11}{15} = \frac{19 \cdot 5}{21 \cdot 5} - \frac{11 \cdot 7}{15 \cdot 7} = \frac{95}{105} - \frac{77}{105} = \frac{95 - 77}{105} = \frac{18}{105} = \frac{6}{35}$$
Ответ:
а) $$\frac{5}{6}$$
б) $$1\frac{7}{12}$$
в) $$\frac{6}{35}$$