From the information given,
The sales tax rate for the state of Washington was 8.3%. Recall, percentage is expressed in terms of 100.
If the cost of a car is $4400
Sales tax = 8.3/100 x 4400
Sales tax = $365.2
Final cost of car = cost of car + sales tax
Final cost of car = 4400 + 365.2
Final cost of car including tax = $4765.2