I am assuming you are asking how many miles you can travel on the taxi.
In this situation a good method would be to make an equation.
Let x represent the number of miles traveled.
The ride costs $2.50 per mile, so the cost of the total trip is equal to 2.5x + 5. (the 5 is the base 5$ cost)
Set this equation equal to 20 as you have $20 to spend.
So, we get
2.5x + 5 = 20
Subtract 5 on both sides to get:
2.5x = 15
Divide by 2.5 on both sides to find x.
x = 6
You can travel 6 miles in the taxi.
