3 1/7 - (19/21 - 1/14) =2 13/42
1) 19/21 - 1/14 = 38/42 - 3/42 = 35/42 = 5/6
2) 3 1/7 - 5/6 = 22/7 - 5/6 = 132/42 - 35/42 =
= 97/42 = 2 13/42
2 4/9 - (1 5/6 - 11/12) = 1 19/36
1) 1 5/6 - 11/12 = 11/6 - 11/12 = 22/12 - 11/12 = 11/12
2) 2 4/9 - 11/12 = 22/9 - 11/12 = 88/36 - 33/36 =
= 55/36 = 1 19/36