Answer:
$182
Step-by-step explanation:
You want to know the cost for 2500 minutes if the cost for 500 minutes is $62, and the cost for 1500 minutes is $122.
The function is said to be linear. This means we can add the cost for an additional 1000 minutes to the cost for 1500 minutes to get the cost for 2500 minutes.
The difference in cost from 1500 minutes to 500 minutes is ...
$122 -62 = $60
So, adding 1000 more minutes to the cost for 1500 minutes will give the cost for 2500 minutes:
$122 +60 = $182
The total monthly cost for using the cell phone for 2500 minutes is $182.
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Additional comment
Effectively, we have found the slope of the cost function to be $60/(1000 minutes) = $0.06/minute.
This means the base cost per month is ...
cost for 1000 minutes = base cost + cost for added 1000 minutes
$92 = base cost + $60
$32 = base cost
Then the cost for 2500 minutes is ...
cost for 2500 minutes = base cost + 2500 × per-minute cost
cost for 2500 minutes = $32 + 2500 × $0.06 = $32 +150 = $182
You will notice we didn't actually need the whole cost function in order to solve the problem. All we needed was the added charge for added minutes. We chose values from the table that let us arrive at 2500 minutes pretty easily: the add-on for 2500 minutes is double the add-on for 1500 minutes starting from the cost for 500 minutes.