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