Flexbox grid: two equal length rows, top row split into two columns
<p>I'm trying to make a layout like the following image using css flexbox.</p>

<p>But I'm not much familiar with flexbox anyone can help me to make this? </p>

<p><a href="https://i.stack.imgur.com/BcGog.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/BcGog.jpg" alt="enter image description here"></a></p>

<p>Here is what I'm trying:</p>

<p><div class="snippet" data-lang="js" data-hide="false" data-console="true" data-babel="false">
<div class="snippet-code">
<pre class="snippet-code-css lang-css prettyprint-override"><code>.row.flex {
    display: flex;
 }

 .row [class=^"col-"] {
  width: 200px;
  height: 100%;
 }</code></pre>
<pre class="snippet-code-html lang-html prettyprint-override"><code>&lt;div class="row flex"&gt;
 &lt;div class="col-xs-12 col-sm-6"&gt;
  
 &lt;/div&gt;
 &lt;div class="col-xs-12 col-sm-6"&gt;
  
 &lt;/div&gt;
 &lt;div class="col-xs-12 col-sm-12"&gt;
  
 &lt;/div&gt;
&lt;/div&gt;</code></pre>
</div>
</div>
</p>

<p>thanks :)</p>