Answer
$ m = 600 \ miles$
Work Step by Step
We write the two equations for total cost:
$ y = 25 + .1m$
OR
$ y = 20 +.25m$
We set the equations equal to each other:
$25 + .1m = 20 + .25m$
Now, we use PEMDAS, a method for simplification. This acronym reminds us that we must first address parentheses, and then exponents. Next, we address multiplication and division, going from left to right. Lastly, we simplify addition and subtraction from left to right. This gives:
$ m = 600 \ miles$