Question 96456
Let x = the amount of 20% copper alloy
20%x+30%(600)=27.5%(x+600)
{{{.20x+.30(600)=.275(x+600)}}}
{{{.20x+180=.275x+165}}}
{{{.20x-.275x+180=.275x+165-.275x}}}
{{{-.075x+180=165}}}
{{{-.075+180-180=165-180}}}
{{{-.075=-15}}}
{{{x=200}}}

x=200 lbs

Good Luck!