First you calculate the amount of the tax on the item.

Then you add together the original cost of the item and the tax.

The easiest way to understand the answer is to turn it around. If you wanted to calculate the item price plus tax, you would multiply the item price by 1.073. So, to back up to the item price from the item price plus tax, divide the item price plus tax by 1.073. $20.00 / 1.073 = item price before sales tax.

Tax

The tax of an item is the money that goes to the poor. Depending on where you live, if your government or president is rich, then the tax amount is bigger. If the government is poor, than there is a low amount of tax on an item.

An excise tax or sales tax is calculated on a per-item basis