1) (2 3/7 - 5 1/4) * 28;

1) (2\frac{3}{7} - 5\frac{1}{4}) \cdot 28 = (\frac{17}{7} - \frac{21}{4}) \cdot 28 = (\frac{68}{28} - \frac{147}{28}) \cdot 28 = -\frac{79}{28} \cdot 28 = -79. 2) (1\frac{2}{9} - 2\frac{20}{33}) \cdot 66 = (\frac{11}{9} - \frac{86}{33}) \cdot 66 = (\frac{121}{99} - \frac{258}{99}) \cdot 66 = -\frac{137}{99} \cdot 66 = -\frac{137}{3} \cdot 2 = -\frac{274}{3} = -91\frac{1}{3}. 3) (\frac{7}{36} - \frac{19}{54} + \frac{5}{27}) : \frac{1}{108} = (\frac{21}{108} - \frac{38}{108} + \frac{20}{108}) : \frac{1}{108} = \frac{3}{108} : \frac{1}{108} = \frac{3}{108} \cdot 108 = 3. 4) (-\frac{1}{18} + 1\frac{7}{12} - 1\frac{3}{8}) : \frac{1}{72} = (-\frac{4}{72} + \frac{13}{12} - \frac{11}{8}) : \frac{1}{72} = (-\frac{4}{72} + \frac{78}{72} - \frac{99}{72}) : \frac{1}{72} = -\frac{25}{72} : \frac{1}{72} = -\frac{25}{72} \cdot 72 = -25.