Answer: She has 525 costumers.
Explanation:
We know that the costumer base is
residential and
business. This means that:
residential customers
Let be "x" the total costumers Athy has and "y" the number of business costumers.
Then "x" must be:

Then, in order to find "y" , we need to multiply the number of residential costumers by
and divide the product by
:

Substituting we get that "x" is:
costumers