<p>First, please note that I mentioned to follow this thought process if there is no time to go through a more conventional way. In this case, I think the traditional algebraic method would not really take that long. </p>
<p>This is what I would pay attention to: I would quickly look at the answers and see if two answers are not really equal or very similar so that they can be excluded. No luck here, but I should notice that three answers are fractions. So, it could be that the three fractions are all wrong and the answer could be D or E. However, the question statement contains the negative power -2/3. So, I'll stick with the fractions and eliminate the answers D and E. I now have three choices: two choices that "look" a tad too simple for a question level 19 and choice A that is in a different form. Also, the negative factor -2/3 is a ... natural to lead towards a "1/something" form. That is why I said that I would have a 90% confidence picking A. In the end, I believe ETS started with the correct answer A, and did not place it in the third position C to avoid rewarding the wild guessers. Then they presented two possible choices (reverse fractions), and finally two excludable answers. </p>
<p>However, working through the problem should not take much longer than this glorified guessing work, especially when seeing the easy reduction of the powers.</p>