Hello there! To find the total cost of anything, add 1 to the tax rate in decimal form and then multiply by the price before tax to get the total cost. 6.5% in decimal form is 0.065. 1 + 0.065 is 1.065. 2,500 * 1.065 is 2,662.5. There. The total cost of the jet ski is $2,662.50.