To determine which unit to use for the x-axis, we need to consider what the x-axis is representing. If the x-axis is measuring time spent commuting, then it should be labeled in minutes. If the x-axis is measuring distance traveled during the commute, then it should be labeled in miles.
If the context suggests that the x-axis represents time, you would use minutes. Conversely, if it represents distance, you would use miles. Based on your question alone, please identify what the x-axis is meant to represent in your graph.