Answer:
$55
Step-by-step explanation:
Let b represent the original bill. The problem statement tells us ...
20% × (b -6) = 9.80
Dividing by 20% gives ...
b -6 = 49.00
b = 55.00 . . . . . . . add 6
Their bill before the discount was $55.00.
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Comment on the tip
It is generally considered better form to tip on the basis of the original bill before coupons and discounts.
