Кнаименьшему общему знаменателю дроби: 5/8 и 1/6 9/13 и 2/21 1/42 и 1/30 7/48 и 11/30 2/3; 1/4 и 5/6 5/6; 2/9 и 7/12

~ 5/8 и 1/6 {5/8*6 и 1/6*8} = 30/48 и 8/48 
~ 9/13 и 2/21 -  невозможно или я туплю  :<
~ 1/42 и 1/30 {1/42*5 и 1/30*7} = 5/210 и 7/210
~ 7/48 и 11/30 {7/48*5 и 11/30*8} = 35/240 и 88/240
~ 2/3; 1/4 и 5/6 {2/3*4; 1/4*3 и 5/6*2} = 8/12; 3/12 и 10/12
~ 5/6; 2/9 и 7/12 {5/6*6; 2/9*4 и 7/12*3} = 30/36; 8/36 и 21/36