Answer:

Step-by-step explanation:
From the question, Diana wants her total bill to be less than $50.
Diana pays a fixed monthly bill of
$39 for her mobile phone and an additional
$0.15 per minute for phone internet service.
The bill Diana pays for m minutes of using the internet is $0.15m in a month.
The total monthly bill becomes,

The maximum bill she wants to pay is $50.

This inequality can be solved to determine the number of available minutes.