199. Найдите значение выражения: 1) (-7/18 + 11/12) : (-19/48); 2) (7/16 - (-5/24)) : (-1 15/16); 3) (10/21 - 25/28) : (-11/14 + 24/35); 4) -2 2/3 + 2 1/3 · (-15 3/7 - (-4.8) : 4/15).

Решение:

1. \( \left(-\frac{7}{18} + \frac{11}{12}\right) : \left(-\frac{19}{48}\right) \)
   \( = \left(-\frac{14}{36} + \frac{33}{36}\right) : \left(-\frac{19}{48}\right) \)
   \( = \frac{19}{36} : \left(-\frac{19}{48}\right) \)
   \( = \frac{19}{36} \cdot \left(-\frac{48}{19}\right) \)
   \( = -\frac{48}{36} \)
   \( = -\frac{4}{3} = -1\frac{1}{3} \)
2. \( \left(\frac{7}{16} - \left(-\frac{5}{24}\right)\right) : \left(-1\frac{15}{16}\right) \)
   \( = \left(\frac{7}{16} + \frac{5}{24}\right) : \left(-\frac{31}{16}\right) \)
   \( = \left(\frac{21}{48} + \frac{10}{48}\right) : \left(-\frac{31}{16}\right) \)
   \( = \frac{31}{48} : \left(-\frac{31}{16}\right) \)
   \( = \frac{31}{48} \cdot \left(-\frac{16}{31}\right) \)
   \( = -\frac{16}{48} \)
   \( = -\frac{1}{3} \)
3. \( \left(\frac{10}{21} - \frac{25}{28}\right) : \left(-\frac{11}{14} + \frac{24}{35}\right) \)
   \( = \left(\frac{40}{84} - \frac{75}{84}\right) : \left(-\frac{55}{70} + \frac{48}{70}\right) \)
   \( = -\frac{35}{84} : \left(-\frac{7}{70}\right) \)
   \( = -\frac{5}{12} : \left(-\frac{1}{10}\right) \)
   \( = \frac{5}{12} \cdot 10 \)
   \( = \frac{50}{12} \)
   \( = \frac{25}{6} = 4\frac{1}{6} \)
4. \( -2\frac{2}{3} + 2\frac{1}{3} \cdot \left(-15\frac{3}{7} - \left(-\frac{48}{10}\right) : \frac{4}{15}\right) \)
   \( = -\frac{8}{3} + \frac{7}{3} \cdot \left(-\frac{108}{7} - \left(-\frac{24}{5}\right) : \frac{4}{15}\right) \)
   \( = -\frac{8}{3} + \frac{7}{3} \cdot \left(-\frac{108}{7} - \left(-\frac{24}{5}\right) \cdot \frac{15}{4}\right) \)
   \( = -\frac{8}{3} + \frac{7}{3} \cdot \left(-\frac{108}{7} - \left(-\frac{6}{1}\right) \cdot 3\right) \)
   \( = -\frac{8}{3} + \frac{7}{3} \cdot \left(-\frac{108}{7} + 18\right) \)
   \( = -\frac{8}{3} + \frac{7}{3} \cdot \left(-\frac{108}{7} + \frac{126}{7}\right) \)
   \( = -\frac{8}{3} + \frac{7}{3} \cdot \frac{18}{7} \)
   \( = -\frac{8}{3} + \frac{18}{3} \)
   \( = -\frac{8}{3} + 6 \)
   \( = -\frac{8}{3} + \frac{18}{3} \)
   \( = \frac{10}{3} = 3\frac{1}{3} \)

Ответ: 1) -1 1/3; 2) -1/3; 3) 4 1/6; 4) 3 1/3.