12 liters of a 12% solution must be mixed with 20% solution to get a 14% solution how many liters of the 20% solution are needed

In a chemistry class, 12L of a 12% alcohol solution must be mixed with a 20% solution to get a 14% solution. How many liters of the 20% solution are needed? 

12% fluid DATA:
amount = 12 liters ; active ingredient = 0.12(12) = 1.44 liters

20% fluid DATA:
amount = x liters ; active ingredient = 0.20x liters


14% fluid DATA:
amount = 12+x liters ; active ingredient = 0.14(12+x)= 1.68+0.14x liters

EQUATION:
active + active = active
1.44 + 0.20x = 1.68+0.14x
0.06x=0.24
x=4 liters (amount of 20% fluid to be added)