Ответ:

Пошаговое объяснение:

3)

(1/2+2/3) / (3/5-2/15) =

(3/6+4/6) / (9/15-2/15) =

7/6 / 7/15 = 7/6 * 15/7 =

15/6 = 5/2 = 2. 1/2

4)

(1/4-1/6) / (3/8-1/3) =

(3/12-2/12) / (9/24-8/24) =

1/12 / 1/24 = 1/12 * 24/1 =

24/12 = 2