The complete question describes the use of word problems to represent inequalities. The $21 means that there is a limit to the number of stops she can take using the train.
The inequality that represents this scenario is:
From the complete question, we have the following parameters:
Initial Fee = $5
Rate per stop = $2.75
Amount = $21
The inequality that represents the scenario is as follows:
Initial Fee + Rate * Number of stops <= Amount
We use <= because the total charges must not exceed the amount.
Let the number of stops be x.
The above formula becomes
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