Question 947061
You can try to fit this two-part mixture problem into one single equation in one variable.


x, how much of the 15% acid to use.
12-x, the quantity of the 30% acid to use.


{{{highlight_green((0.15x+0.3(12-x))/12=0.22)}}}
;
simplify and solve for x.
-
{{{15x+30(12-x)=12*22}}}
{{{15x+30*12-30x=12*22}}}
{{{-15x+30*12=22*12}}}
{{{-15x=22*12-30*12}}}
{{{15x=30*12-22*12}}}
{{{15x=8*12}}}
{{{5x=8*4}}}
{{{x=32/5}}}
{{{highlight(x=6&2/5)}}} ounces


You can study how this would work using two variables if you want.
<a href="http://www.algebra.com/my/Mixtures%3A-All-in-Symbols.lesson?content_action=show_dev">Mixing two concentrations for known amount of mixture</a>