Let us take a sharp point for the graph.
In 4 hours total earning is $30.
Therefore, earnings per hours would be 30/4 = $7.5 per hour.
Are given direct variation between Total earnings(E) and Number of hours worked(h).
So, we can setup a direct variation as
Total earnings = Earning each hour * Number of hours.
Therefore, direct variation function would be
E=7.5*h.
Therefore, the direct variation function between E, the total earnings in dollars, and h, the number of hours worked is E = 7.5h.