Question 423888
let x litters of the 14% solution.
Then we obtain x+20 litters of  the 30%.
The pure alcohol litters before and after mixing must be equal.
So we obtain an equation
{{{(14/100)*x+(50/100)*20=(30/100)*(x+20)}}}
{{{14/100*x+50/100*20=30/100*(x+20)}}}
Multiply by 100
{{{14x+50*20=30(x+20)}}}
{{{14x+1000=30x+600}}}
{{{1000-600=30x-14}}}
{{{400=16x}}}
{{{16x=400}}}
Divide by 16
{{{x=400/16}}}
x=25
So 25 litters 14% needed.