So for part (A) you will look at the total amount of the haircut which is $22.00 and the discount of 0.25%.
The math there will be asking "what is 25 % of 22" (the answer is $5.50). You can also figure it out by doing 22.00 * 0.25 (this is will still come out to be $5.50). So the total bill with the discount will be ($16.50). How to get that is you will take $22.00 - $5.50 ($16.50 hair cut with the discount).
Now she is going to leave a tip, now remember, her current total is $16.50 because she got a discount. So you will follow the same math, 20% of $16.50 is $3.30. In this case you will add, $16.50 + $3.30 = $19.80. So her final amount is going to be $19.80.
A - $16.50
B - $19.80
