Jan went grocery shopping and only bought items which had been marked down. The items she bought, along with their prices, can be seen below. Item Final Price Markdown Chicken $8.47 15% Milk $2.16 20% Onions $0.89 10% Potato chips $1.45 12% Oranges $1.36 25% Flour $4.39 18% Compared to if she had bought no items on sale, by what percent was Jan’s total grocery bill discounted? Round to two decimal places. a. 15.85% b. 16.50% c. 16.65% d. 17.50%

I copied your table and added one column and one line.
It is all explained below.

Item               Final Price    Markdown   Original Price
Chicken         $8.47            15%             $9.96
Milk               $2.16             20%             $2.70
Onions          $0.89             10%             $0.99
Potato chips  $1.45             12%             $1.65
Oranges        $1.36             25%             $1.81
Flour             $4.39             18%              $5.35
Totals          $18.72                                $22.46

First, find each original price. To do that, change the markdown into a decimal. Then subtract it from 1. Then divide the discounted price by it. For example, for the chicken, the markdown is 15%. Change it to 0.15. Then 1 - 0.15 = 0.85. Now divide $8.47 by 0.85, and the original price is $9.96. I did that for all items and added the last column to the table above.

Now you add the discounted prices and add the original prices. I wrote them as the last line in the table above. Now you need to know what is the overall percent discount. Divide the total discounted price by the total original price.
18.72/22.46 = 0.83348 = 83.35%
The discounted price is 83.35% of the original price.
The original price is 100% of the original price.
The original price was 100% of the original price. The discounted price is 83.35% of the original price. Now subtract 100% - 18.35% = 16.65%.
The overall markdown was 16.65%