For this case we have the following function:

The first thing you should do is graph the function to see the behavior.
When observing the graph (in the attached image) we observe that the following point belongs to the graph:

To prove it, let's evaluate the point in the function:

The equation is fulfilled and therefore the point belongs to the graph.
Answer:
(6.2, 7.4)
See attached image
If you are trying to find tax, the answer is $23.67,
But if you are trying to find the total price, the answer is $292.67
814,180. Hope I helped. If i didn't I am sos sorry. I would take 7.9 or .079 to 754,844 to get your number.