Inverse functions can be used to find prices before taxes, discounts, extra charges, and other things.

Let's look at the following retail example.

A clerk needs to price an laptop returned by a customer. The customer paid a total of $343.44, which included a desktop cleanup charge of $20 and 8% sales tax. What price should the clerk mark on the tag?

First we need to write the equation for the total cost as a function of price. Let c represent cost and p represent price.

In a real-world situation, you would not switch the variables because they are named for specific quantities, but what you found is the inverse function.

Now we can calculate the original price of the digital camera. Since c = 343.44, the total price the customer paid for the digital camera, we can evaluate the inverse function for c = 343.44. See below.

Therefore the clerk should mark the price tag for the camera as $298.