Answer
Mixture:
400 mL of the first solution,
600 mL of the second solution.
Work Step by Step
Let x be mililiters taken of the first solution,
and y be mililiters taken of the second solution.
Then, since 1L=1000mL
$x+y=1000$,
and 14% of 1000mL=140mL, so
$0.05x+0.20y=140\quad/\times 100$
$5x+20y=14000$
$\left\{\begin{array}{ll}
x+y=1000 & /\times(-5) \\
5x+20y=14,000 &
\end{array}\right. $
(eliminates x)
$\left\{\begin{array}{ll}
-5x-5y=-5000 & \\
5x+20y=14,000 & /add
\end{array}\right.$
$15y=9,000\quad/\div 15$
$y=600$
Back-substitute
$x+y=1000$
$x+600=1000\quad/-600$
$x=400$
Mixture:
400 mL of the first solution
600 mL of the second solution
