Question 1000909
<pre>
You are forgetting to multiply the 50% or .5 by the 20 gallons 
and you are only putting .5 instead of .5(20)

That is, you have this:

.3x+.8y=.5
x+y=20 

but you should have this:

.3x+.8y=.5(20)
x+y=20 

Now try it.

Edwin</pre>