Answer:
About 5 miles
Explanation:
At first, I thought it would be 6 miles because 6x3 is 18 plus the initial 6 dollars which is 24. However, it says that it does not include the tip, which means that Mike DID tip the driver. So there has to be some space for the tip. If it was 6 miles it would be 24 dollars, but there is no more space for the tip. So it has to be 5 miles, because that will be 21 dollars, and assuming the tip could be about 3 dollars, then that would total up to 24 dollars.