<PRE><B>Question 1016083</B>
One material quantity is known and the other is unknown.


Let x be the ounces of the 28% chocolate.


{{{chocolate/mixture=40percent}}}


{{{(9*56+28x)/(x+9)=40}}}


STEPS
{{{56*9+28x=40(x+9)}}}
{{{56*9+28x=40x+360}}}
{{{40x-28x=56*9-360}}}
{{{12x=56*9-360}}}
{{{x=(56*9-120*3)/12}}}
{{{x=(7*8*3*3-120*3)/12}}}
{{{x=14*3-30}}}
{{{highlight(x=12)}}}



See also the lesson, http://www.algebra.com/my/Two-Part-Mixture-with-one-material-quantity-unknown.lesson?content_action=show_dev</PRE>