Ответ:

Пошаговое объяснение:

1)

х÷7=4÷21

21х = 7 * 4

21х = 28

х = 28 : 21

х= 4/3

х = 1 1/3

2)

3 1/3÷х=4 4/13÷1 2/26

4 4/13х = 3 1/3 * 1 2/26

56/13х = 10/3 * 28/26

56/13х = 140/39

х = 140/39 : 56/13

х = 140/39 * 13/56

х= 5/6

Пошаговое объяснение:

х : 7 = 4 : 21

х * 21 = 7 * 4

21х = 28

х = 28 : 21

х = 28/21

х = 4/3

х = 1. 1/3

3. 1/3 : х = 4. 4/13 : 1. 2/26

10/3 : х = 56/13 : 28/26

56/13 * х = 28/26 * 10/3

56/13х = 28/13 * 5/3

56/13х = 140/39

х = 140/39 : 56/13

х = 140/39 * 13/56

х = 5/3 * 1/2

х = 5/6