Question 653262
The total cost of anything is (cost + (tax*cost)).  For example:

What's the total cost of a book that is $15 with a 5% tax?
A: 15 + (.05*15) or $15.75.

In your problem, you're given the final cost after tax and the tax %.  So, your equation would be the same as above, just with different variables filled in:

843 = cost + (.08*cost)
843 = C + .08C  (shortened "cost" to "C")
843 = 1.08C (added 1C + .08C)

Now, we can divide both sides by 1.08:
780.56 = Cost

The dryer list price (before tax) was $780.56.