The x axis is time in hours, and the y axis is the charge in dollars.
She does not charge a fee for the first hour, so a point on the graph is (1, 0).
After the first hour, she charges $75/hour, so the slope is 75.
Because this is a constant rate of $75/hour, the graph will be linear (a straight line).
At the second hour, the client is charged $75. This point is (2, 75).
Since the graph will be a straight line, and you have two points (1, 0) and (2, 75) you can draw the graph (since two points form a line).
As always, please comment with any questions!