Answer :
the alcohol concentration of the mixture is 12%
Explanation:concentration for the 20 gallons = 15%
concentration for the 30 gallons = 10%
let the concentration of the alcohol mixture = y
concentration × amount for 20 gallons + concentration × amount for the 30 gallons = concentration of the mixture × total gallons
Total gallons = 20 + 30 = 50
15% × 20 + 10% × 30 = y × 50
0.15 × 20 + 0.1 × 30 = 50y
3 + 3 = 50y
6 = 50y
y = 6/50
y = 0.12
y = 0.12 = 12/100 = 12%
Hence, the alcohol concentration of the mixture is 12%