We need to set up an equation to solve this problem. The sales tax is a percentage of the total, so that's what we are looking for.
Let's call S our sales tax
So, that's what we are looking for, and we are given the actual sales tax
So now we have a decimal. In order to convert a decimal into a percentage, we must multiply by 100 (since percentages are out of 100)
The sales tax rate is 3.8%