In an 8-gram solution of water and alcohol, the ratio by mass of water to alcohol is 3 to 1. If 12 grams of a solution consisting of 2 grams water for each gram of alcohol is added to the 8-gram solution, what fraction by mass of the new solution is alcohol? -- I know that the first thing you should do is try to find the mass of alcohol in both the 8-gram and the 12-gram solution. However, to find the amount of alcohol in the 8-gram solution why would you multiply it by 1/4 and not 1/3? Its just confusing how the ratios can be written like 1:3 and then 1/4?