Description: Budgeting money is one of the most valuable math skills you'll learn. Practice with us as we figure out how much money is left after a cab fare. Created by Sal Khan. The taxi fare includes a base charge of $2.50 as soon as you enter the cab, plus an additional $2.50 per mile traveled. If Sandy starts off with a $20 bill, takes the cab for five miles, and leaves a $1 tip, how much money will she be left with? Well she's going to go for 5 miles times $2.50 per miles.*Teacher Advisor is 100% free.