Question 1080825
{{{(5*36)/(5+x)=12}}}


{{{180/(x+5)=12}}}

{{{12x+60=180}}}

{{{12x=120}}}

{{{x=10}}}



Also look at 36% compared to 12%.
Concentration cut to one-third.  Increase only the volume by 3, but to not change the total quantity of soap.  Fifteen total finished liters, so 15-5=10.