:1/2+6ц3/7, 6+4ц9/11, 2/9+1ц8/15, 12ц5/9-7ц1/6, 7ц1/4-3ц7/15, 9ц5/12-6ц2/7

1/2+6 3/7=7/14+6 6/14=6 13/14
6+4 9/11=10 9/11
2/9 + 1 8/15= 10/45+1 24/45= 1 34/45
12 5/9 -7 1/6 =12 10/18-7 3/18=5 7/18
7 1/4-3 7/15=7 15/60-3 28/60=6 75/60-3 28/60=3 47/60
9 5/12- 6 2/7=9 35/84-6 24/84=3 11/84