Smart #s -the only way?

[Ceej05]

Reposting question in (hopefully) correct location.
In Guide 1 of MGMAT, on pg. 84, there is problem about the two libraries combining portions of their books. I tried solving without a smart # but can't make it work.

I tried 1/3 A + (1/4 of 2a) to get the combined proportion of books. I then simplified the 1/4 of 2a to a/2. With 1/3 a + 1/2 a, I got 5/6 A. Where is this equation incorrect?

[RonPurewal]

nope, wrong location. questions about material from the MGMAT guides belong in the MGMAT non-CAT folder.

also, per the forum rules, you need to post the entire question exactly as originally written (including the answer choices, if there are any).
without the question, this thread is essentially useless for other readers; moreover, we don't always, or even usually, have the books available when moderating the forum.

so... please post the entire problem, and do so in the correct folder. thanks.