1. The problem is to find the formula to calculate sales tax. 2. Sales tax is a percentage of the price of an item that is added to the original price. 3. The formula to calculate sales tax is: $$\text{Sales Tax} = \text{Price} \times \frac{\text{Tax Rate}}{100}$$ 4. Here, \text{Price} is the original cost of the item, and \text{Tax Rate} is the sales tax percentage. 5. To find the total price including tax, use: $$\text{Total Price} = \text{Price} + \text{Sales Tax} = \text{Price} \times \left(1 + \frac{\text{Tax Rate}}{100}\right)$$ 6. Important rules: - Always convert the tax rate percentage to a decimal by dividing by 100. - Multiply the price by this decimal to get the sales tax amount. - Add the sales tax to the original price to get the total cost. This formula helps you calculate how much extra you pay due to sales tax.