There are several information's already given in the question. based on those given information's the answer can be easily deduced.
Price at which Jan bought the blazer = $39.90
Actual price of the blazer = $38
Then
Sales tax charged on the blazer = 39.90 - 38.00
= 1.90 dollars
I hope the above procedure is clear enough for you to understand and this was the answer that you were looking for.
