A mixture of chlorine and water contains a total of 60 gallons. There are 30 gallons of pure Chlorine in the mixture. (I) what percent of the mixture is water? (ii) what percent of the mixture is chlorine?

60 gallons of the whole thing, chlorine and water mixed.

one may note that 30 is half of 60, namely 50% of 60.

if there are 30 gallons of chlorine, 60 - 30, the leftover is 30 gallons, and that must be water.

so 50% is chlorine, and the other 50% is water.