Question 1048585
How much alcohol all by itself?  How much mixture?  What concentration of alcohol wanted?


Do you know how much of the 15% and the 55% alcohols?  No.
Give them each a variable.  You can also just assign a variable to exactly ONE of them and use the given  560 mL mixture to find variable expression for the other alcohol solution.  If you want to see how this works (but using a different example) then study this:


<a href="https://www.youtube.com/watch?v=-REjxT9KCzQ">Finding both quantities of two-part mixture - video example lesson</a>