Ответ:

Решение:

  1. а) \(\frac{3}{7}-\frac{3}{14}=\frac{6-3}{14}=\frac{3}{14}\);
    б) \(\frac{3}{4}-\frac{5}{12}=\frac{9-5}{12}=\frac{1}{3}\);
    в) \(6\frac{13}{28}+\frac{1}{7}=6\frac{13}{28}+\frac{4}{28}=6\frac{17}{28}\).
  2. а) \(\frac{3}{7}-\frac{1}{9}=\frac{27-7}{63}=\frac{20}{63}\);
    б) \(\frac{5}{6}+\frac{4}{11}=\frac{55+24}{66}=\frac{79}{66}=1\frac{13}{66}\);
    в) \(8\frac{1}{31}-1\frac{3}{4}=\frac{249}{31}-\frac{7}{4}=\frac{996-217}{124}=\frac{779}{124}=6\frac{35}{124}\).
  3. а) \(\frac{5}{42}-\frac{17}{70}=\frac{25-51}{210}=-\frac{26}{210}=-\frac{13}{105}\);
    б) \(3\frac{1}{30}-5\frac{7}{60}=3\frac{2}{60}-5\frac{7}{60}=-2\frac{5}{60}=-2\frac{1}{12}\);
    в) \(\frac{7}{16}-2\frac{23}{32}=\frac{14}{32}-2\frac{23}{32}=-2\frac{9}{32}\).

Ответ: 1) а) \(\frac{3}{14}\); б) \(\frac{1}{3}\); в) \(6\frac{17}{28}\). 2) а) \(\frac{20}{63}\); б) \(1\frac{13}{66}\); в) \(6\frac{35}{124}\). 3) а) \(-\frac{13}{105}\); б) \(-2\frac{1}{12}\); в) \(-2\frac{9}{32}\).