To convert the percentage to a decimal, move the decimal point 2 places to the left.
7.8% becomes 0.078 as a decimal.
Now multiply the cost of the dvd player by that to find the amount of sales tax, then add that to the price for the total cost.
285 x 0.078 = 22.23 ( amount of tax)
Total cost: 285 + 22.23 = $307.23