Answer:
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