Final answer:
To find Nan's total bill for the $85 dress on sale at 25% off with 5% sales tax, calculate the discount amount, subtract it from the original price to get the discounted price, calculate the sales tax amount, and then add the discounted price and sales tax together.
Step-by-step explanation:
To find the total bill, we first need to calculate the amount of the discount that Nan received on the dress. Since the dress was on sale at 25% off the original price, we can find the discount amount by multiplying the original price by 0.25. So, the discount is 85 * 0.25 = 21.25.
The discounted price of the dress is the original price minus the discount, so the discounted price is 85 - 21.25 = 63.75.
Next, we need to calculate the amount of sales tax. Nan paid 5% sales tax, so we can find the sales tax amount by multiplying the discounted price by 0.05. So, the sales tax is 63.75 * 0.05 = 3.1875.
To find the total bill, we add the discounted price and the sales tax: 63.75 + 3.1875 = 66.9375.
Finally, we can round the total bill to the nearest dollar to get the final answer: 66.94.