1/ 3 - ( + 2 / 3 ) = : - 2/ 5 - ( - 3 / 5 ) = : - 2/ 5 - ( - 3 / 5 ) = : -3/ 7 - ( + 4 / 7 ) = : 5 /8-(-7/8)= : - 1 / 9 - ( + 2 / 9) =
1/3-2/3=-1/3 -2/5+3/5=1/5 -3/7-4/7=-7/7=-1 5/8+7/8=12/8=3/2=1 1/2 -1/9-2/9=-3/9=-1/3