Ответ:

  1. НОЗ(12, 18) = 36. Приводим дроби: \(\frac{5}{12}=\frac{15}{36}\), \(\frac{7}{18}=\frac{14}{36}\).
  2. НОЗ(8, 12) = 24. \(\frac{3}{8}=\frac{9}{24}\), \(\frac{5}{12}=\frac{10}{24}\).
  3. НОЗ(15, 20) = 60. \(\frac{2}{15}=\frac{8}{60}\), \(\frac{7}{20}=\frac{21}{60}\).
  4. НОЗ(14, 21) = 42. \(\frac{5}{14}=\frac{15}{42}\), \(\frac{3}{21}=\frac{6}{42}\).
  5. НОЗ(9, 6, 12) = 36. \(\frac{4}{9}=\frac{16}{36}\), \(\frac{5}{6}=\frac{30}{36}\), \(\frac{7}{12}=\frac{21}{36}\).