5/7 = (5·2)/(7·2) = 10/14, 1/2 = (1·7)/(2·7) = 7/14;
7/20 = (7·3)/(20·3) = 21/60, 1/15 = (1·4)/(15·4) = 4/60.
5/7 = (5·2)/(7·2) = 10/14, 1/2 = (1·7)/(2·7) = 7/14;
7/20 = (7·3)/(20·3) = 21/60, 1/15 = (1·4)/(15·4) = 4/60.