Решение примеров:

1)

$$18\frac{5}{12} - \frac{7}{12} \cdot 1\frac{19}{21} - \frac{17}{72} \cdot \frac{2}{3} = \frac{221}{12} - \frac{7}{12} \cdot \frac{40}{21} - \frac{17}{72} \cdot \frac{2}{3} = \frac{221}{12} - \frac{2}{9} - \frac{17}{108} = \frac{221 \cdot 9 - 2 \cdot 12 - 17}{108} = \frac{1989 - 24 - 17}{108} = \frac{1948}{108} = \frac{487}{27} = 18\frac{1}{27}$$

Ответ: $$18\frac{1}{27}$$

2)

$$\left(6\frac{3}{4} - 5\frac{1}{8} : 1\frac{9}{32}\right) \cdot \frac{5}{11} = \left(\frac{27}{4} - \frac{41}{8} : \frac{41}{32}\right) \cdot \frac{5}{11} = \left(\frac{27}{4} - \frac{41}{8} \cdot \frac{32}{41}\right) \cdot \frac{5}{11} = \left(\frac{27}{4} - 4\right) \cdot \frac{5}{11} = \left(\frac{27}{4} - \frac{16}{4}\right) \cdot \frac{5}{11} = \frac{11}{4} \cdot \frac{5}{11} = \frac{5}{4} = 1\frac{1}{4}$$

Ответ: $$1\frac{1}{4}$$

3)

$$(-1,42 - (-3,22)) : (-0,4) + (-6) \cdot (-0,7) = (-1,42 + 3,22) : (-0,4) + 4,2 = 1,8 : (-0,4) + 4,2 = -4,5 + 4,2 = -0,3$$

Ответ: $$-0,3$$

4)

$$\left(-\frac{7}{18} + \frac{11}{12}\right) : \left(-\frac{19}{48}\right) = \left(-\frac{14}{36} + \frac{33}{36}\right) : \left(-\frac{19}{48}\right) = \frac{19}{36} : \left(-\frac{19}{48}\right) = \frac{19}{36} \cdot \left(-\frac{48}{19}\right) = -\frac{48}{36} = -\frac{4}{3} = -1\frac{1}{3}$$

Ответ: $$-1\frac{1}{3}$$

5)

$$\left(-3\frac{1}{12} - 2\frac{1}{15}\right) : \left(-5\frac{3}{20}\right) = \left(-\frac{37}{12} - \frac{31}{15}\right) : \left(-\frac{103}{20}\right) = \left(-\frac{37 \cdot 5 - 31 \cdot 4}{60}\right) : \left(-\frac{103}{20}\right) = \left(-\frac{185 - 124}{60}\right) : \left(-\frac{103}{20}\right) = -\frac{61}{60} : \left(-\frac{103}{20}\right) = \frac{61}{60} \cdot \frac{20}{103} = \frac{61}{3 \cdot 103} = \frac{61}{309}$$

Ответ: $$\frac{61}{309}$$