Let amount of 15% solution be x
Amount of 65% solution is 5L
So after mixing both concentration solutions the net volume will be (5+x).
We could write the following equation:
[tex]\begin{gathered} 15x+65(5)=(5+x)\cdot25 \\ 15x+325=125+25x \\ 200=10x \\ x=20 \end{gathered}[/tex]Therefore, the correct option is B. 20 liters.
