Answer:
$115 per month.
Explanation:
If we check the difference between the total costs from one month to the next, we can find the monthly fee.
In month one, the money spent includes the one-time fee and the monthly fee.
In month two, the total money spent includes both of those and another monthly fee.
Find the difference to find the monthly fee paid in month 2.
380 - 265 = 115.
115 must be the monthly fee.
To check this, let's subtract the difference in total cost in months 2 and 3.
495 - 380 = 115.
Perfect. It checks out.
The cost per month, then, is $115 per month.