title: Xpath select only part of an attribute
body: <p>if</p>
  
  <pre><code>/dt/@id
  </code></pre>
  
  <p>returns <code>comment_34232</code> or <code>comment_12</code> how can I make it return <code>34232</code> or <code>12</code> (in other words replaceing <code>'comment_'</code> with <code>''</code></p>
  
  <p>and if </p>
  
  <pre><code>/span/style
  </code></pre>
  
  <p>returns <code>width: 80%;</code> how can I replace  <code>width:</code> and after that <code>%;</code> to retrieve <code>80</code></p>
  
  <p>Regards</p>