1. 12 23/26 - (6 12/26+4 3/26) = 2 4/13
1) 6 12/26 + 4 3/26 = 10 15/26
2) 12 23/26 - 10 15/26 = 2 8/26 = 2 4/13
2. 5 8/21+(13 6/21-9 19/21) = 8 16/21
1) 13 6/21 - 9 19/21 = 3 8/21
2) 5 8/21 + 3 8/21 = 8 16/21
