State sales tax is based on retail price. An item that sells for $115.99 has a sales tax of $8.12. Find a mathematical model that gives the amount of sales tax y in terms of the retail price x. (Round the coefficient to two decimal places.)

y =

Use the model to find the sales tax on a $530.50 purchase. (Round your answer to the nearest cent.)
$

2 answers

rate = 8.12/115.99 = .070006035
but since the $8.12 was most likely rounded off to the nearest cent, I would say it was .07 or 7%