<PRE><B>Question 334816</B>
Let A be the number of liters of 40%-alcohol solution.
Look at the concentration equation.
{{{(40/100)A+(80/100)(10)=(60/100)(A+10)}}}
{{{40A+800=60(A+10)}}}
{{{40A+800=60A+600}}}
{{{-20A=-200}}}
{{{A=10}}}
.
.
.
10 liters of 40% solution plus 10 liters of 80% will provide 20 liters of 60% solution. 
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