A graph is discrete if it can only take specific values. It is continuous if it consists of connected lines or curves. Let's consider the given graph.
Patty pays for one train ride at the time and the price for it is Therefore, the graph consists of distinct and unconnected points and it is discrete.
The domain is the number of train rides Patty takes. They are the whole numbers from to Since she pays for each ride, her balance can be any multiple of from to