Question 73047
Let x=number of liters of 20% solution, y=# of liters of 10% solution
If we want 50 liters of the combined sum of the 2 solutions it will look like this
{{{x+y=50}}}
Since we want 50 liters of 12% solution it comes to 
{{{50*0.12=6}}}
And to mix the solutions we use the equation (for instance 30% of 10 liters + 20% of 10 liters = 5 liters, this is an example not the answer)
{{{0.2x+0.1y=6}}}
Now use the linear solver to get our answer
*[invoke linear "x", "y", 1, 1, 50, .2, .1, 6 ]
So we want 10 liters of 20% solution and 40 liters of 10% solution