Пошаговое объяснение:

10/17 - 4/17 = (10 - 4)/17 = 6/17

12/23 - 9/23 = (12 - 9)/23 = 3/23

21/40 - 7/40 = (21 - 7)/40 = 14/40 = 7/20

36/60 - 36/60 = 0