S = sale price (in dollars) p = sticker price (in dollars) Note: the sticker price is what the customer pays after the discount Another note: This is ignoring any taxes or other fees
We're told that the sale price is the result of taking 10% off the sticker price. This means...
sale price = (sticker price) - (10% of sticker price) s = p - 0.10*p s = 1*p - 0.10*p s = (1 - 0.10)*p s = (0.90)*p s = 0.90*p
So the expression for the sale price is 0.90*p where p is the sticker price in dollars.
Note: this means that the sale price is 90% of the sticker price.
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Now plug in the sticker price p = 80 to find the sale price s s = 0.90*p s = 0.90*80 s = 72
The sale price is $72 which is what the customer will pay (if we ignore any taxes or other fees).
