Question 773670
Let v = the volume in quarts of the current solution to remove from the radiator and replace.  

{{{(25*60-v*60+v*0)/(25)=40}}}
{{{(25*60-60*v)/25=40}}}
{{{25*6-6*v=100}}}
{{{-6v=100-150}}}
{{{6v=50}}}
{{{v=8&1/3}}} quarts