[jennacat]

so the question is: You choose to make a serial dilution of alcohols ie. to make the 2nd dilution from the 1st.  In order to end up with 140mL of 82% AND 52mL of 51%, how many mL of absolute ethanol do you need to make up the 1st solution? (answers to 2 d.p.)

I've never really done these kinda of questions with alcohol involved so i think its the percentages that are throwing me off and i'm kinda confused what the question is asking. how do i go about solving this?

[Aldebaran]

This isn’t really a question of chemistry but of simple maths. The question doesn’t make it clear whether the proportions are  by weight or volume or a combination but to keep it simple assume volume and ask yourself what will be the total volume of alcohol present in the final solutions and work back from there.