Answer:
Let x= liters of 18% solution to be added to a 10% solution.
20-x= liters of 10% solution to be mixed with 18% solution.
..
18%(x)+10%(20-x)=15%(20)
.18x+2-.1x=3
..08x=1
x=1/.08=12.5
ans:
12.5 liters of an 18% alcohol solution must be added to a 10% alcohol solution to get 20 L of a 15% acohol solution.
I hope it's helpful!
