The sales tax on a sofa that cost $575 was $43.13. what was the percent sales tax?

It is important to look at all details given in the question very carefully.
Amount of sales tax taken on the sofa = $43.13
Actual cost of the sofa = $575
Let us assume the percentage of sales tax taken = x%
Then
(x/100) * 575 = 43.13
5.75x = 43.13
x = 43.13/5.75
   = 7.50 percent
So the percentage of sales tax charged for the sofa was 7.50%.I hope the procedure is clear enough for you to understand. Based on this procedure, similar problems can be done with absolute ease.