The original price was $82.
-- The dealer knocked ($82 - $65.60) = $16.40 off of the price because
he loves his customers so much and he wanted to make their lives easier.
-- The amount he knocked off is ( 16.40 / 82 ) = 0.2 = 20% of the original price.
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Check:
If he reduced the original price 20%, then 80% of it must have been left.
80% of the original price = 0.8 x $82 = $65.60
I hoped i help :)