So let's call this equation one and this equation two. We can now take equation two and substitute this quantity into this quantity. So the delta S of the surroundings is equal to negative of the Delta H system divided by the temperature. So we replace this quantity with the right side of this equation, and we get equation three. So the change in entropy of our system is minus the change in entropy of the system divided by the temperature, which is the same thing as the change in entropy of our surroundings is equal to the change in entropy of our universe. Let's call this equation three.