ANSWER:
Water: 80 gallons
Premium antifreeze: 240 gallons
STEP-BY-STEP EXPLANATION:
Given:
Let x amount of water required
An equation based on the the percent water, an 80% solution is 20% water.
Therefore, we can establish the following equation:
[tex]\begin{gathered} 0.2\cdot(320-x)+x=0.4\cdot320 \\ \text{ solving for x:} \\ 64-0.2x+x=128 \\ 0.8x=128-64 \\ x=\frac{64}{0.8} \\ x=80\text{ gallons} \end{gathered}[/tex]So that's 80 gallons of water and that's 240 (320-80) gallons of premium antifreeze.