4.190 Выполните сложение: a) -4/7 + (-2/7); б) -3/7 + (-3/4); в) -5/9 + (-7/8); г) -2 2/9 + (-5 5/18); д) -3 3/5 + (-5,9); e) -2 1/6 + (-4,75).

a) $$-\frac{4}{7} + \left(-\frac{2}{7}\right) = -\frac{4}{7} - \frac{2}{7} = -\frac{6}{7}$$ б) $$-\frac{3}{7} + \left(-\frac{3}{4}\right) = -\frac{3}{7} - \frac{3}{4} = -\frac{3 \cdot 4}{7 \cdot 4} - \frac{3 \cdot 7}{4 \cdot 7} = -\frac{12}{28} - \frac{21}{28} = -\frac{33}{28} = -1\frac{5}{28}$$ в) $$-\frac{5}{9} + \left(-\frac{7}{8}\right) = -\frac{5}{9} - \frac{7}{8} = -\frac{5 \cdot 8}{9 \cdot 8} - \frac{7 \cdot 9}{8 \cdot 9} = -\frac{40}{72} - \frac{63}{72} = -\frac{103}{72} = -1\frac{31}{72}$$ г) $$-2\frac{2}{9} + \left(-5\frac{5}{18}\right) = -2\frac{4}{18} - 5\frac{5}{18} = -7\frac{9}{18} = -7\frac{1}{2}$$ д) $$-3\frac{3}{5} + (-5,9) = -3,6 - 5,9 = -9,5$$ e) $$-2\frac{1}{6} + (-4,75) = -2\frac{1}{6} - 4,75 = -2\frac{1}{6} - 4\frac{3}{4} = -2\frac{2}{12} - 4\frac{9}{12} = -6\frac{11}{12}$$