4. Вычислите: a) - \frac{4}{9} + (-\frac{5}{36}) б) - \frac{7}{7} - \frac{2}{21} в) \frac{7}{88} + (-\frac{12}{121}) г) 1 \frac{5}{24} - \frac{3}{36} д) \frac{5}{6} + (-\frac{8}{21})

Решим задачу 4: а) - \frac{4}{9} + (-\frac{5}{36}) = - \frac{4}{9} - \frac{5}{36} = - \frac{16}{36} - \frac{5}{36} = - \frac{21}{36} = - \frac{7}{12} б) - \frac{7}{7} - \frac{2}{21} = -1 - \frac{2}{21} = - \frac{21}{21} - \frac{2}{21} = - \frac{23}{21} = -1 \frac{2}{21} в) \frac{7}{88} + (-\frac{12}{121}) = \frac{7}{88} - \frac{12}{121} = \frac{7 \cdot 11}{88 \cdot 11} - \frac{12 \cdot 8}{121 \cdot 8} = \frac{77}{968} - \frac{96}{968} = - \frac{19}{968} г) 1 \frac{5}{24} - \frac{3}{36} = \frac{29}{24} - \frac{1}{12} = \frac{29}{24} - \frac{2}{24} = \frac{27}{24} = \frac{9}{8} = 1 \frac{1}{8} д) \frac{5}{6} + (-\frac{8}{21}) = \frac{5}{6} - \frac{8}{21} = \frac{5 \cdot 7}{6 \cdot 7} - \frac{8 \cdot 2}{21 \cdot 2} = \frac{35}{42} - \frac{16}{42} = \frac{19}{42}