The total bill before taxes or gratuities was $80 for the steak + $10 for the wine = $80+$10 = $<<80+10=90>>90
If the tax is 10%, then the taxes paid were $90 * 10% = $<<90*10*.01=9>>9
That means that the total bill before gratuities was $90 + $9 = $<<90+9=99>>99
If the final bill was $140, then you were charged $140-$99 = $<<140-99=41>>41 for gratuities
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