title: Images not changing size with flex
body: <p>I am unable to change the size of my article images with flex. I'm new to flex (and new to coding) and have read this: <a href="https://css-tricks.com/snippets/css/a-guide-to-flexbox/" rel="nofollow noreferrer">https://css-tricks.com/snippets/css/a-guide-to-flexbox/</a> but still can't solve my issue. I'd appreciate some guidance. Thanks!</p>
  
  <p>CSS</p>
  
  <pre><code>.prezi-container {
    display: flex;
    flex-wrap: wrap;
  }
  
  article {
    flex: 1 1 100%;
  }
  </code></pre>
  
  <p>HTML</p>
  
  <pre><code>&lt;section class="prezi-container"&gt;
    &lt;article&gt;
      &lt;a href="http://www.domain/image1.com"&gt;
        &lt;img class="presentation" src="images/image1" alt="Some alt text."&gt;
      &lt;/a&gt;
      &lt;h4&gt;Title&lt;/h4&gt;
      &lt;p&gt;Click image to see presentation.&lt;/p&gt;
    &lt;/article&gt;
    &lt;article&gt;
      &lt;a href="http://www.domain/image2.com"&gt;
        &lt;img class="presentation" src="images/image2" alt="Some alt text."&gt;
      &lt;/a&gt;
      &lt;h4&gt;Title&lt;/h4&gt;
      &lt;p&gt;Click image to see presentation.&lt;/p&gt;
    &lt;/article&gt;
     &lt;article&gt;
      &lt;a href="http://www.domain/image3.com"&gt;
        &lt;img class="presentation" src="images/image3" alt="Some alt text."&gt;
      &lt;/a&gt;
      &lt;h4&gt;Title&lt;/h4&gt;
      &lt;p&gt;Click image to see presentation.&lt;/p&gt;
    &lt;/article&gt;
   &lt;/section&gt;
  </code></pre>