Let's use the variable x to represent the number of hours walking the dog and the variable y to represent the number of hours washing cars.
If he can work a maximum of 15 hours, we have the inequality:
Also, if he wants to make at least $75, we have the inequality:
In order to graph these inequalities, let's find two points that are on the line of the corresponding equation:
Now, graphing each inequation with the corresponding solution area (first one in blue, second one in green, common region in orange), we have:
Analysing the options, two of them that are inside the solution area are 4 hrs dog walking and 8 hrs car washing (A) and 10 hrs dog walking and 3 hrs car washing (C).