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