nThe left side of the equation describes the change in state caused by the path quantities on the right side of the equation.
nProblem: A chicken coup starts the year with 34,000 chickens. During the year, 16,000 chicks are purchased, 20,000 chickens are sold, 12,000 eggs hatch, and 20 chickens are eaten by foxes. How many chickens are present at the end of the year? (See Figure 17.12)