Answer: $0.75
Step-by-step explanation: To find the brand of sunscreen with the greatest cost per fluid ounce, we need to calculate the cost per fluid ounce for each brand by dividing the cost by the number of fluid ounces per bottle.
For brand W, the cost per fluid ounce is:
12 dollars / 20 fluid ounces = 0.6 dollars per fluid ounce
For brand X, the cost per fluid ounce is:
11.25 dollars / 15 fluid ounces = 0.75 dollars per fluid ounce
For brand Y, the cost per fluid ounce is:
6.50 dollars / 10 fluid ounces = 0.65 dollars per fluid ounce
For brand Z, the cost per fluid ounce is:
2.50 dollars / 5 fluid ounces = 0.5 dollars per fluid ounce
Therefore, brand X has the greatest cost per fluid ounce, at 0.75 dollars per fluid ounce.