Hey there!
Basically it wants you to add 3 and 8 from each other, what ever the answer to that part, you multiply the result by 9
Here this is what i meant

Or you could do this method too!

They both give you the result of 
So, I am assuming your expression would look like this: 
Good luck on your assignment and enjoy your day!
~
The answer to this question is 0.4
Since sales tax goes after the discount, it would be 3 dollars and 20 cents. Taking 50 dollars and 20% is discounted (50*.2), which would be 10 dollars taken off. It would be 40 dollars shoes and then you apply sales tax by multiplying 40 by .08, giving you the amount of tax paid.