The title means: eating in a restaurant, lunch is $4.00, and sales tax is $0.24. So how much tax do you have to pay for dinner at $ 15.00? (You can ignore the $ sign when answering questions.)

Solution:

This is a matter of proportion, and the proportion of sales tax to sales is certain. therefore

0.24: 4 = tax payable: 15

The tax payable for dinner is 0.24× 15/4 = 0.9 (USD).

If you don't use the proportion, you can ask for a tax rate of 0.24÷4 first.

Therefore, the tax payable is 0.24÷4× 15 = 0.9 (USD).