Answer:
the 7% tax rate
Step-by-step explanation:
Since the tip was 20% of the amount including tax, we don't need to know the tax rate to figure the total amount.
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The bill before tip was $3.50/0.20 = $17.50, so the total amount including tax and tip was $17.50 +3.50 = $21.00.
(Tax rate doesn't figure in, unless we want to know the bill before tax was added. As it works out, these numbers don't add up. The bill with tax would be either 17.49 or 17.51. It cannot be 17.50.)
