You are looking at the HTML representation of the XML format.
HTML is good for debugging, but is unsuitable for application use.
Specify the format parameter to change the output format.
To see the non HTML representation of the XML format, set format=xml.
See the complete documentation, or API help for more information. 
<?xml version="1.0"?>
<api>
  <query-continue>
    <allimages gaicontinue="1236805_536624206408608_1122518083_n.jpg" />
  </query-continue>
  <query>
    <pages>
      <page pageid="4225" ns="6" title="File:-74 Sam Jones - Arrow International Racing.jpg" />
      <page pageid="4224" ns="6" title="File:-95 Mike Bell - Arrow International Racing.jpg" />
      <page pageid="171" ns="6" title="File:1.jpg" />
      <page pageid="4403" ns="6" title="File:10888741 799118803482558 4720721381885387613 n.jpg">
        <duplicatefiles>
          <df name="Klaidas.jpg" user="Marius van wyk" timestamp="2015-07-13T12:11:28Z" />
        </duplicatefiles>
      </page>
      <page pageid="4438" ns="6" title="File:11252023 1611432502406203 2144480493159048887 o.jpg" />
      <page pageid="3770" ns="6" title="File:1184839 584422098266042 1283064256 n.jpg" />
      <page pageid="4675" ns="6" title="File:1190.png" />
      <page pageid="3410" ns="6" title="File:11 constant italy.png" />
      <page pageid="382" ns="6" title="File:11tdr.jpg" />
      <page pageid="4606" ns="6" title="File:12287140 10206070072805477 98748479 o.jpg" />
    </pages>
  </query>
</api>