Question 715739
Amount of Silver divided by amount of alloy equals 12%.


x the 9% Silver.  y the 14% Silver.

{{{(9x+14y)/10=12}}} and {{{x+y=10}}}.


Use the rational percent equation first.  
9x+14y=120


The system to solve is this:
{{{highlight(9x+14y=120)}}}
{{{highlight(x+y=10)}}}

Try elimination.  Multiply second equation by 9 and subtract from first equation.  Solve for value of y.
9x+14y-9x-9y=120-90
5y=30
{{{highlight(y=6)}}}  kg of the 14% alloy


Use the second equation, the mass equation, to get the value for x.  
{{{highlight(x=4)}}}  kg of the 9% alloy