Answer:
7
Step-by-step explanation:
The graph that is drawn here shows the altitude as a function of time. When the plane takes off from Chicago, the graph will start from the horizontal axis.
Next, when the plane takes 3 intermediate stops, altitude will touch the horizontal axis 3 times.
Next, when the plane lands in New York the altitude will touch the horizontal axis.
Next, when plane takes off from New York and takes an intermediate stop, altitude will touch horizontal axis.
Lastly the altitude will touch the axis when plane lands back in Chicago.
So, cumulatively the altitude will touch the horizontal axis seven times.
