Question 5363
Let x = amount of pure water at 100% water

60 = solution being mixed at 20% water

x+60 = resulting mixture at 30% water.


From this, the equation is:
1.00(x) + (.20)(60) = (.30)(x+ 60) 
1.00x + 1.20 = .30x + 1.80


Appropriate simplification gives you 
.70x = .60
{{{x =.60/.70 = 6/7}}} oz.


It usually comes out more even than this, but sometimes life is like that.  I think it's right.  Anybody see an error?


R^2 at SCC