3/5-4/5=
2/7-(-3/7)=
-1/9-(5/9)=
6/7-8/7=
3/9-(-2/9)=
-5/8-(-3/8)=
-1/12-(-5/12)=
2/15-7/15=
4/9-5/9=

3/5-4/5=2/7-(-3/7)=2/7+3/7=5/7-1/9-(5/9)=-1/9-5/9=-6/9=-2/36/7-8/7==-2/73/9-(-2/9)=3/9+2/9=5/9-5/8-(-3/8)=-5/8+3/8=-2/8=-1/4-1/12-(-5/12)=-1/12+5/12=4/12=1/32/15-7/15=-2/154/9-5/9=-1/9