<p>To answer your specific question, as the comments already stated, <strong>no</strong> you can not accept an answer to a different question. So in light of that, reasonable actions to take are:</p>

<ol>
<li>Flag your question to be merged with the duplicate. </li>
<li>Answer <em>your own</em> question, given the information in the other. </li>
</ol>

<p>As Nick Cox says in the comments make sure to link to the other question, both for sake of proper attribution as well as creating a strong indicator between the two questions. (The linked and related questions bars on the right hand side are wonderful for navigating similar questions.)</p>

<p>Given the disruption that occurs when merging questions together - especially if your question already has an answer(s) to it - I would prefer option 2 unless the questions are flagrantly duplicate.</p>
