# Differential Mixing Problem

At time $$t=0$$, a tank contains 30 oz of salt dissolved in 100 gallons of water. Then brine containing 8oz of salt per gallon of brine is allowed to enter the tank at a rate of 2 gal/min and the mixed solution is drained from the tank at the same rate.

How much salt is in the tank at an arbitrary time?

So the way I write the differential is $$\frac{dS}{dt}=S_{in}-S_{out}$$, where $$S_{in}$$ is the rate of salt going in and $$S_{out}$$ is the rate of salt coming out. The differential I obtained is $$\frac{dS}{dt}=16-\frac{3}{50}S$$ and the solution to be $$S=\frac{800}{3}-\frac{7991}{3}e^{\frac{-3t}{50}}$$. I'm unsure of what went wrong but the webwork keeps rejecting my answers.