British sterling silver is a copper-silver alloy that is 7.5% copper by weight. how many grams of pure copper and how many grams of british sterling silver should be used to prepare 250 grams of a copper-silver alloy that is 20% copper by weight? (round your answers to one decimal place.)

The answer to your question is: 200 g

Explanation:

Need 250 gr of copper.silver alloy 20% copper by weight

                     250 g alloy     100%

                           x                20%

                         x = 20(250)100

                        x = 5000 / 100

                        x = 50 g of copper

Then

   g of British sterling silver = 250 g alloy - 50 g of copper

   g of British sterling silver = 200 g