Answer:
[ where 
is number of months]
Step-by-step explanation:
Pool pass cost for first month =$30
Pool pass cost after first month = $15 for each month
The total amount charged by the pool can be expressed as a function 
where represents the number of months.
This can be simplified by using distribution.
Take 15 as greatest common factor.
∴
For 
∴ Amount charged by pool for 12 months = $195
I don't think those two expressions would even be equal unless w = 0. You can't just add in a 2 from nowhere.
Answer: Approximately 390,244 people per square mile
Work Shown:
Density = population/area
Density = (8 million people)/(20.5 square miles)
Density = 390,243.9024 approximately
This rounds to 390,244 since we're talking about the number of people.
