## Algebra: A Combined Approach (4th Edition)

Let $x$ be the volume of 20% solution needed. Let $y$ be the volume of 70% solution needed. Because 50 litres is needed, $x+y=50$ 20%=0.2; 60%=0.6; 70%=0.7 To make 50 litres of 60% solution using 20% and 70% solutions, $0.2x+0.7y=0.6(50)$ $0.2x+0.7y=30$ $x+y=50$ $0.2x+0.7y=30$ $x+y=50$ $x=50-y$ $0.2x+0.7y=30$ $0.2(50-y)+0.7y=30$ $10-0.2y+0.7y=30$ $10+0.5y=30$ $0.5y=20$ $y=40$ $x+y=50$ $x=50-y$ $x=50-(40)$ $x=10$ $x=10$ $y=40$ 10 litres of 20% solution. 40 litres of 70% solution.