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Let the original price be x.
Then after first reduction the price is
x - 0.2x = x*(1-0.2) = 0.8x.
Next, after the second reduction, the price is
0.8x - 0.15*(0.8x)) = 0.8x*(1-0.15) = 0.8x*0.85 = 0.8*0.85x = 0.68x.
You are given that
0.68x = 170 dollars.
Hence, x = = 250.
ANSWER. The original price was 250 dollars.
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Then you have a problem like this one with the chain of discounts, it is important to understand that the final
discounted price is the product of the original price and some number of simple factors.
You must know what these factors are and how to solve such problems quickly in couple of lines (and a couple of minutes).
Learn it from my post.
In this problem, the first factor is 1-0.2 = 0.8; the second factor is 1-0.15 = 0.85.
So, each factor is the complement of a discount value (presented as decimal) to 1.