1/3 и 1/2, общий знаменатель 3*2 = 6, 1/3 = 2/6 и 1/2= 3/6
2/5 и 3/4, 4*5 =20, 2/5 = 8/20 и 3/4 = 15/20
1/2 и 1/7, 2*7 = 14, 1/2 = 7/14 и 1/7 = 2/14
2/7 и 5/6, 7*6=42, 2/7 = 12/42 и 5/6 =35/42
7/9 и 3/4, 9*4 = 36, 7/9 = 28/36 и 3/4 = 27/36
5/16 и 5/8, 16 :8 =2, общий знаменатель 16, 5/16 и 5/8 = 10/16
9/10 и 1/20, 20 : 10 = 2, общий знаменатель 20, 9/10 = 18/20 и 1/20