Mixture \(A\) is \(20\) percent alcohol, and mixture \(B\) is \(50\) percent alcohol. If the two are poured together to create a \(15\)-gallon mixture that contains \(30\) percent alcohol, approximately how many gallons of mixture \(A\) are in the mixture?

(A) 3 gallons
(B) 4 gallons
(C) 5 gallons
(D) 10 gallons
(E) 12 gallons

Answer: D

Source: Veritas Prep