ratio and percentage question

Question

13.5 liters of fuel containing 2.2% oil is available for a certain two-cycle engine. This fuel is to be used for another engine requiring a 4.1% oil mixture. How many liters of oil must be added?

Answer 1

.022(13.5) +x = .041(x+13.5)

x=0.267 liters of 0il= a little over a 1/4 of a Liter