We need to set up a system of equations. One will represent the total mass of the alloy in terms of the sum of each individual alloy. The other equation will be an expression of the total concentration of the alloy in terms of each individual alloy's concentration. We don't know the mass of either the 15% copper or the 70% copper alloy. Let's call them x and y, respectively. Then one equation is:
x + y = 50
The other equation will be:
.15x + .70y = .48(50)
You should now be able to solve this system of equations by either the Substitution or Elimination Method, Ryan
