Answer:
Hours
Explanation:
Jake is being paid $15 an hour, not per child.
Say he has five children, three stay for one hour, two stay for two hours. If he's getting paid per hour, then he'd earn $105. But, if he gets paid per child he'd only make $75 dollars.
But since it says that he gets paid per HOUR, it would be proportional to how much money he makes.