А) 7/21 +1/7
Б) 8/24 -1/6
В) 5/7+1/3
Г) 8/9 -3

7/21 + 1/7 = 7/21 + 3/21 = 10/218/24 - 1/6 = 8/24 - 4/24 = 4/24 = 1/65/7 + 1/3 = 15/21 + 7/21 = 22/218/9 - 3 = 8/9 - 27/9 = - 19/9