SOLUTION: I need help with the following problem...I have NO idea what to do!! Thanks in advance for your help!!! Anne and Nancy use a metal alloy that is 15.9% copper to make jewelry. Ho

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Question 144560: I need help with the following problem...I have NO idea what to do!! Thanks in advance for your help!!!
Anne and Nancy use a metal alloy that is 15.9% copper to make jewelry. How many ounces of an alloy that is 15% copper must be mixed with an alloy that is 18% copper to form 90 ounces of the desired alloy?

Answer by checkley77(12844) About Me  (Show Source):
You can put this solution on YOUR website!
.15x+.18(90-x)=.159*90
.15x+16.2-.18x=14.31
-.03x=14.31-16.2
-.03x=-1.89
x=-1.89/-.03
x=63 oz. of 155 copper is needed.
90-63=27 oz. of 18% copper is needed.
proof:
.15*63+.18*27=14.31
9.45+4.86=14.31
14.31=14.31