Anne and Nancy use a metal alloy that is 20.45% copper to make jewelry. How many ounces of a 12% alloy must be mixed with a 25% alloy to form 100 ounces of the desired alloy?

Answer 1

amount of 12% stuff ---- x
amount of the other stuff ---- 100-x

solve for x:

.12x + .25(100-x) = .2045(100)