23. Среди дробей 5/10; 10/20; 7/21; 6/18; 3/9; 12/24; 25/50; 21/63 найдите дроби, равные 1/2 и 1/3.

Сократим дроби:

\(\frac{5}{10}=\frac{1}{2}\), \(\frac{10}{20}=\frac{1}{2}\), \(\frac{12}{24}=\frac{1}{2}\), \(\frac{25}{50}=\frac{1}{2}\).

\(\frac{7}{21}=\frac{1}{3}\), \(\frac{6}{18}=\frac{1}{3}\), \(\frac{3}{9}=\frac{1}{3}\), \(\frac{21}{63}=\frac{1}{3}\).

Ответ: \(1/2\): 5/10, 10/20, 12/24, 25/50; \(1/3\): 7/21, 6/18, 3/9, 21/63.