1) 7/15-2/5 2)11/21-3/14 3)6/7-9/14 4)9/20-5/12 5)5/9-3/8 6)7/9-5/12 7)7/18-1/45 8)11/42-5/28

1) 7/15 - 2/5 = 7/15 - 6/15 = 1/15

2) 11/21 - 3/14 = 22/42 - 9/42 = 13/42

3) 6/7 - 9/14 = 12/14 - 9/14 = 3/14

4) 9/20 - 5/12 = 27/60 - 25/60 = 2/60 = 1/30

5) 5/9 - 3/8 = 40/72 - 27/72 = 13/72

6) 7/9 - 5/12 = 28/36 - 15/36 = 13/36

7) 7/18 - 1/45 = 35/90 - 2/90 = 33/90 = 11/30

8) 11/42 - 5/28 = 22/84 - 15/84 = 7/84 = 1/12