Question 946767
Let x=% concentration in resulting alloy

Now we know that the amount of pure silver that exists before the mixture takes place (0.7(25)+0.2(45)) has to equal the amount of pure silver in the final mixture(x(70)).
Sooooo
0.7(25)+0.2(45)=x(70)
17.5+9=x(70)
x=(26.5)/70=~38%
Hope this helps----ptaylor