Пошаговое объяснение:

9/15 = (9:3)/(15:3) = 3/5

8/12 = (8:4)/(12:4) = 2/3

28/35 = (28:7)/(35:7) = 4/5

15/3 = (15:3)/(3:3) = 5/1 = 5

39/91 = (39:13)/(91:13) = 3/7

250/1000 = (250:250)/(1000:250) = 1/4

60/144 = (60:12)/(144:12) = 5/12

55/4000 = (55:5)/(4000 : 5) = 11/800