a) 10 Salad Dressing.
Explanation
- Determine the percentage of customers who choose Italian dressing from the graph, which is 40%.
- Determine the percentage of customers who choose Vinaigrette dressing from the graph, which is 30%.
- Calculate the difference in percentage between Italian dressing and Vinaigrette dressing, which is 40% – 30% = 10%.
- Convert the percentage difference to a number by multiplying it by the total number of customers, which is 200. So, 10% * 200 = 20.