I'm pretty sure I marked this one wrong - but while revising the solution today morning after solving this last evening, I could see where I went wrong, so my explanation will be basis that.
I like to assume numbers for such one, only because variables scare me, and number make the logic simpler for me. I also like to humanize the objects of the question for my own understanding.
A painter mixes two batches of paint to create a customer color. Batch A (Amber) has a gloss concentration of G% by volume. Batch B (Brown) has a gloss percentage of H% by volume. The painter combines M litres of Amber with N litres of Brown.
Now for the statements.
Statement I: The ratio of the gloss concentration in Amber to Brown is 7 to 5. Let's assume this translates to 35% to 20%, to relate things better. For us to find the percentage in the mixture, we still need to know in what quantity were each of the paints mixed. For instance, if we assume 35% for Amber, and 20% for Brown, but if Amber is just a litre, but Brown is four, the resultant ratio will be different than if it is, say, Amber two litres and Brown three. Hence, Statement I is not enough.
Statement II: The ratio of the quantity of Amber paint mixed with Brown paint is 3 to 4. Without the ratio of the volume of gloss concentration, however, we cannot find the gloss concentration for the resultant mixture. For instance, if Amber only has 10% of gloss, versus 80% for Brown, the proportions will be quite different than if both have 50% ratios.
Both together: If we assume 3 litres of Amber is added to 4 Litres of Brown, with Amber having, say, a 7% concentration of gloss and Brown having a 5% concentration, we can define what the resulting ratio is - 5.86%.
But this what I failed to consider:
If we assume 3 litres of Amber is added to 4 litres of Brown, with Amber having, say, a 35% concentration to a 20$ concentration of Brown, we can define the resulting ratio as 26.2%
So, two (and more) answers, hence, E. Clearly, one way to solve this would've been to know the concentration percentage rather than the ratio used.
Bunuel
A painter mixes two batches of paint to create a custom color. Batch A has a gloss finish concentration of G% by volume. Batch B has a gloss finish concentration of H% by volume. The painter combines M liters of Batch A with N liters of Batch B. What is the gloss finish percentage, by volume, of the resulting mixture?
(1) The ratio of G to H is 7 to 5.
(2) The ratio of M to N is 3 to 4.