title: Special method in ruby (question mark)
body: <p>How do you define a method of verification? 
  The example: include? even? odd?</p>
  
  <pre><code>&gt;&gt; 2.odd?
  =&gt; false
  &gt;&gt; 6.even?
  =&gt; true
  &gt;&gt; 
  </code></pre>