For this case, what you should keep in mind are the following considerations:
1) Rewrite the expressions correctly using the properties of the exponents: Addition, multiplication, division, subtraction and negative exponents.
2) Simplify the expression as much as possible.
Answer:
See attached image.
The answer is 6$ because 50% of 40 would be 20 and 50% of 20 is 10 but when you all on the tax which would be around a dollar when you take 50% of 10 which is 5 and add on the tax which is a dollar you then get 6$ in total.
1= 15
2= 12
Hope this helps