[15 points, just check for equation]
sterling silver is an alloy of 92.5% silver and 7.5% copper by weight. you have 15 ounces of 800 grade silver which is 80% silver and 20% copper. how much pure silver should you add to the 800 grade to make sterling silver?

is the equation for copper 0.075(15 + s) = 3 + s?

No; 0.075(15 + s) = 3; s = 25 oz

Step-by-step explanation:

No, but you are close.

The mass of copper in your 800 grade silver is

Mass = 0.20 × 15  = 3 oz

You are adding s oz of silver so that 7.5 % of the total mass is still 3 oz of copper.

The equation becomes

0.075(15 + s) = 3      Divide both sides by 0.075

           15 + s = 40     Subtract 15 from each side

                  s = 25 oz

You add 25 oz of silver to your 800 grade alloy to get sterling .

Check:

0.075(15 + 25) = 3

    0.075 × 40 = 3

                    3 = 3

55

step-by-step explanation: