As we see in the graph Gavin earns 20$ per hour and Eva earns 23$ every two hours.
First, we must figure out how much Eva made in an hour
23 ÷ 2hours = 11.5
Now we subtract to find the difference
20$ (Gavins) - 11.5$ (Evas) = 8.50
Gavins by $8.50 is your answer