Answer
$x+y=30 \\ 0.25 x+0.5 y=12$
Work Step by Step
Let $x$ and $y$ be the number of liters in the $25 \%$ solution and $50 \%$ solution, respectively.
The system of two equations is:
$x+y=30 \\ 0.25 x+0.5 y=12$
Substitute the value of $x=880$ into the second equation to get the value of $y$.
$y=880+80 $
Thus, $y=960$
