oblicz :
12 - 13 2/5 =
8 2/3 - (- 6 2/3) =
-3 5/7 - 6 7/8 =
10 3/5 - 11 5/7 =
- 8 4/9 - 13 5/6 =
- 6 1/4 - ( - 3 3/8) =
- 7 5/6 - (-10 1/7) =​