<PRE><B>Question 1084611</B>
x ounces of 20% copper 
mix with 
400 ounces of 80% copper
to get
(x+400) ounces of 50% copper

set up the equation, solve for x 
0.2x+0.8(400)=0.5(x+400)

x = 400 ounces
if you input x in the equation, it equals on both side.

if you have any alternative solution, i would love to hear.
adamchen894@gmail.com</PRE>