Answer:
The answer is 28%
Explanation:
So no matter what size bottle you have fill 71.43% of it with the 70/30 mix of isopropyl alcohol and the rest with water. If you want to determine the percentage of water just take the difference between the 71.43% and a full bottle which is represented by 1. Each bottle should then contain 28.57% distilled water no matter what size the bottle is.