If the total fare was $21.50, then that is what it will all have to equal out to.
They charged a pick-up fee of $3.10. Which means that no matter how far you go, you will pay that. Then an extra $2 per mile. If m is mile, then it would be 2m because it is $2 per extra mile. Then add the pick-up fee of $3.10 and you will get your answer of $21.50=3.10+2m.
