Brass is made from a mixture of copper and other elements. A mixture that is 80% copper is combined with a mixture that is 60% copper, resulting in 100 pounds of brass that is 65% copper.Which equation can be used to find x, the amount of 60% mixture used to create the 65% mixture?

Let x be the pounds of the 60% copper mixture. Since the final amount is 100 pounds, the amount of the 80% mixture is 100 − x pounds. The copper contributed by the two mixtures is 0.6x and 0.8(100 − x), and together they must equal 65% of 100 pounds, or 100(0.65). This is choice A.

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