From the given graph it is clear that it is a graph of greatest integer function because the we have open circles on the right side of each floor and closed circle on the left side of each floor.
The given graph is defined as
Graph of greatest integer function shifts 2 units up.
Explanation: The equation is in slope-intercept form, y=mx+b. Since it is parallel to the equation, it has the same slope (2/3x) and since b is the x intercept, b is 9.