в) \(\frac{5}{7}\) и \(\frac{5}{8}\); г) \(\frac{19}{57}\) и \(\frac{7}{21}\)

Решение:

в) \(\frac{5}{7} = \frac{40}{56}\), \(\frac{5}{8} = \frac{35}{56}\). \(\frac{35}{56} < \frac{40}{56}\), значит \(\frac{5}{8} < \frac{5}{7}\).

г) \(\frac{19}{57} = \frac{1}{3}\), \(\frac{7}{21} = \frac{1}{3}\). \(\frac{1}{3} = \frac{1}{3}\), значит \(\frac{19}{57} = \frac{7}{21}\).

Ответ: в) \(\frac{5}{8}\) меньше \(\frac{5}{7}\); г) \(\frac{19}{57}\) равно \(\frac{7}{21}\).