4.257 Вычислите! a) $$-\frac{4}{3} - \left(-\frac{2}{9}\right)$$; б) $$5\frac{2}{7} - 6\frac{5}{14}$$; в) $$-2\frac{3}{16} + \frac{5}{8}$$; д) $$\frac{17}{30} - (-0,6)$$; ж) $$12,5 - 7\frac{3}{4}$$; з) $$-3\frac{1}{7} - (-4,2)$$.

a) $$-\frac{4}{3} - \left(-\frac{2}{9}\right) = -\frac{4}{3} + \frac{2}{9} = -\frac{12}{9} + \frac{2}{9} = -\frac{10}{9} = -1\frac{1}{9}$$. б) $$5\frac{2}{7} - 6\frac{5}{14} = \frac{37}{7} - \frac{89}{14} = \frac{74}{14} - \frac{89}{14} = -\frac{15}{14} = -1\frac{1}{14}$$. в) $$-2\frac{3}{16} + \frac{5}{8} = -\frac{35}{16} + \frac{10}{16} = -\frac{25}{16} = -1\frac{9}{16}$$. д) $$\frac{17}{30} - (-0,6) = \frac{17}{30} + 0,6 = \frac{17}{30} + \frac{6}{10} = \frac{17}{30} + \frac{18}{30} = \frac{35}{30} = \frac{7}{6} = 1\frac{1}{6}$$. ж) $$12,5 - 7\frac{3}{4} = \frac{25}{2} - \frac{31}{4} = \frac{50}{4} - \frac{31}{4} = \frac{19}{4} = 4\frac{3}{4}$$. з) $$-3\frac{1}{7} - (-4,2) = -3\frac{1}{7} + 4,2 = -\frac{22}{7} + \frac{42}{10} = -\frac{22}{7} + \frac{21}{5} = -\frac{110}{35} + \frac{147}{35} = \frac{37}{35} = 1\frac{2}{35}$$.