Question 714727
x ml. of 10% solution and y ml. of 18% solution, want 12% result, 112 ml. size.


{{{(10x+18y)/112=12}}} AND {{{x+y=112}}}


The percentage equation:
{{{(5x+9y)/56=12}}}
{{{5x+9y=672}}}


System to solve is:
{{{5x+9y=672}}}
{{{x+y=112}}}


Multiply second equation by 5 and subtract from first equation.
{{{5x+9y-5(x+y)=672-5*112}}}
{{{9y-5y=112}}}
{{{4y=112}}}
{{{highlight(y=28)}}} ml. of the 18% hydrogen peroxide solution.


Now, you can find x, using x+y=112.