Ответ:

1)16

2)15

3)3

4)49

Пошаговое объяснение:

1) x/4 = 28/7

x = 4 * 4

x = 16

2) 1/3 = 5/x

x = 5*3

x = 15

3) 8/x = 64/24

64x = 24*8

8x = 24

x = 3

4) 7/8 = x/56

56*7 = 8x

7*7 = x

x = 49