Ответ:

4.

12/16 = 3/4

30/45 = 2/3

5.

3/4 = 9/12 = 15/20

Пошаговое объяснение:

4.

12/16 = 12:4/16:4 = 3/4

30/45 = 30:15/45:15 = 2/3

5.

3/4 = 3x3/4x3 = 9/12 = 3x5/4x5 = 15/20