An empty fuel tank with a capacity of 218 gallons was filled partially with fuel A and then to capacity with fuel B. Fuel A contains 12% ethanol by volume and fuel B contains 16% ethanol by volume. If the full fuel tank contains 30 gallons of ethanol, how many gallons of fuel A were added?  Choose the correct choice from the following options
A) 122
B) 150
C) 100
D) 80
E) 50

Rationale: "say there are a gallons of fuel a in the tank , then there would be 218 - a gallons of fuel b . the amount of ethanol in a gallons of fuel a is 0.12 a ; the amount of ethanol in 218 - a gallons of fuel b is 0.16 ( 218 - a ) ; since the total amount of ethanol is 30 gallons then 0.12 a + 0.16 ( 218 - a ) = 30 - - > a = 122 . answer : a ."
Answer: A