Diners frequently add a 15% tip when charging a meal to a credit card. What is the price of the meal without the tip if the amount charged is 13.80. How much was the tip

12

Step-by-step explanation:

In this question, it means that the price of 13.80 is inclusive of the tip. This means that the price is 115% of the normal price. Then we must ask ourselves, if the price of 13.80 is 115%, what is 100%?

That is,

13.80 = 115%

? = 100%

We work it out as follows:

(100/115) * 13.80

= 12