Once again, treating the differential like a quantity, which it really isn't a quantity. You really have to view this as a limit of that change in P over change in time. The limit as we get smaller and smaller and smaller changes in time. But once again, for the sake of this, we can do this. And when we do that, we would be left with one over P dP is equal to K dt. Now we can integrate both sides. Because this was a separable differential equation, we were able to completely separate the P's and dP's from the things involving T's, or I guess the things that aren't involving P's.