sterling silver is 92.5% silver and 7.5% copper. one silver-copper alloy is 95.0% silver, and a second silver-copper alloy is 80.0% silver. how much of each sould be used in order to make 100 g of sterling silver? let the mass of the silver-copper alloy with 95.0% silver be x and the mass of the silver-copper alloy with 80.0% be y.