SOLUTION: An instrument store gives a 10% discount to all students off the original cost of an instrument. During a back to school sale an additional 15% is taken off the discounted price. J

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The original price was x. So after the 10% discount the price was . That price was then discounted 15%, so the price is now , but we know this expression is equal to $306, because that is what was paid. So:









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If the original price was 400, the 10% discount price would have been 400 - 40 = 360, then the 15% discount would have been 360 * .15 = 54, so the final price would be 360 - 54 = 306. Checks.