Answer:
6 hours; each paying $20
Step-by-step explanation:
To start off, we know that Marissa paid exactly $20 for parking. Since we know that Marissa and Haylie paid the same amount, we must now move on to Haylie.
Haylie paid $5 upfront. Now we must figure out how many hours Haylie must have stayed if each hour costed $2.50. We can figure this out by dividing $15 by $2.50 since Haylie already paid $5 upfront.
$15 / $2.50 = 6
This means that Haylie and Marissa stayed for 6 hours and paid exactly $20 dollars each.