5/7+3 6/7 1 6/11-7/11 9/15+7/15 9-3 7/8 6 6/13-5 11/13 2 15/19+1 5/19 1 5/7-6/7 19/21+9/21 9 1/7-2 5/7 6 8/9+7 5/9 6/7+5/7 5 3/8-3 7 9/17+8 8/17 9 3/13-8 9/13 1 6/11-7/11

5/7 + 3 6/7= 3 11/7=4 3/7
16/11-7/11=9/11
9/15+7/15=16/15=1 1/15
9-3 7/8=9/1-31/8=72-31/8=41/8=5 1/8
6 6/13-5 11/13=84/13-76/13=8/13
2 15/19+15/19=2 30/19=3 11/19
15/7-6/7=9/7=1 2/7
19/21+9/21=28/21=1 7/21
9 1/7-2 5/7=64/7-19/7=45/7=6 3/7
5 3/8-3= 2 3/8
7 9/17+8 8/17= 15 17/17=16
9 3/13-8 9/13= 120/13-113/13=7/13
16/11-7/11=9/11