Suppose there is a tank full of 300 gallons of pure water, and water containing one pound per gallon of a chemical is flowing in at rate of 3 gallons per minute, while the perfectly mixed solution is flowing out at a rate of 6 gallons per minute. My equation is set up like this:

$\displaystyle \frac{dQ}{dt}+\frac{6}{300-3t}Q=3,\; Q(0)=0$

Is this correct? Because I don't seem to be getting an answer that makes sense.