Решение

1) a) $$\frac{3}{4} + \frac{5}{12} = \frac{3 \cdot 3 + 5}{12} = \frac{9 + 5}{12} = \frac{14}{12} = \frac{7}{6} = 1\frac{1}{6}$$.

Ответ: $$1\frac{1}{6}$$

2) a) $$1\frac{2}{5} - 4\frac{1}{12} = \frac{7}{5} - \frac{49}{12} = \frac{7 \cdot 12 - 49 \cdot 5}{5 \cdot 12} = \frac{84 - 245}{60} = \frac{-161}{60} = -2\frac{41}{60}$$.

Ответ: $$-2\frac{41}{60}$$

3) a) $$\frac{1}{5} : \frac{3}{41} = -\frac{1}{5} \cdot \frac{41}{3} = -\frac{41}{15} = -2\frac{11}{15}$$.

Ответ: $$-2\frac{11}{15}$$