I don't want to write over it. Well, I'll just write 20x. And on the left-hand side, it is 20x. And then on the right-hand side, let's see, this cancels with that. We have xy plus 10y. And now let me take the derivative of both sides with respect to time. So the derivative of 20 times something with respect to time is going to be the derivative of 20 times something with respect to the something, which is just 20.