Final answer:
The independent variable in the situation where a taxi driver charges an initial fee plus a fee per mile is the number of miles driven, as it can vary independently and determines the total cost.
Step-by-step explanation:
In the given situation where a taxi driver charges an initial fee of $2.00 plus $0.30 per mile, the independent variable is the number of miles driven. This is because the total charge is dependent on the number of miles, and the miles can vary independently of the initial fee.
The driver does not control the distance; rather, the passenger decides how many miles they need to travel, hence making the miles traveled the independent variable.