<PRE><B>Question 620192</B>
The formula for a concentrated mixture is &lt;P&gt;

% times gallons (1) + % times gallons (2) / gallons (1+2) = New mixture %.&lt;P&gt;

{{{(.8x + 100*.3)/(100 + x) = .7}}}&lt;P&gt;

.8x + 30 = 70 + .7x&lt;P&gt;
.1x = 40&lt;P&gt;
x = 400
&lt;P&gt;Hope the solution helped.  Sometimes you need more than a solution.  Contact fcabanski@hotmail.com for online, private tutoring, or personalized problem solving (quick for groups of problems.)</PRE>