Calculo del termino desconocido en una proporcion

1) 5.12 = x6

60 = x6

60 = 6x 
 6      6 

X = 10

2) 4x = 18.2

4x = 36

4x = 36
 4      4

X = 9

3) x49 = 7.7

x49 = 49

x49 = 49
49      49

X = 1

4) 5.4 = 10x

20 = 10x

20 = 10x
10     10

X = 10

5) 25.4 = x50

100 = x50

100 = 50x
 50      50

X = 2