What is the value of X

30 is to 25     as    4x-4  is to 20

30/25  =  (4x-4) / 20 

1/       25 / 20 = 30 / 4x-4

2/       20 / 25 = 4x-4 / 30

3/       30 / 25 = 4x-4 / 20

4/       25 / 30 = 20 / 4x-4