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="A3.png" />
  </query-continue>
  <query>
    <pages>
      <page pageid="120" ns="6" title="Arquivo:1238980 10201914935464914 964089819 n.jpg" />
      <page pageid="716" ns="6" title="Arquivo:1 Formulário.jpg" />
      <page pageid="727" ns="6" title="Arquivo:1 formulário.jpg" />
      <page pageid="118" ns="6" title="Arquivo:23930 109333645747616 8134040 n.jpg" />
      <page pageid="721" ns="6" title="Arquivo:2 Formulário.jpg">
        <duplicatefiles>
          <df name="2_formulário.jpg" user="Ingrid" timestamp="2015-12-15T11:57:18Z" />
          <df name="Segundo_formulário.jpg" user="Ingrid" timestamp="2015-12-15T15:52:30Z" />
        </duplicatefiles>
      </page>
      <page pageid="728" ns="6" title="Arquivo:2 formulário.jpg">
        <duplicatefiles>
          <df name="2_Formulário.jpg" user="Ingrid" timestamp="2015-12-15T15:51:12Z" />
          <df name="Segundo_formulário.jpg" user="Ingrid" timestamp="2015-12-15T15:52:30Z" />
        </duplicatefiles>
      </page>
      <page pageid="121" ns="6" title="Arquivo:339309 331121370307486 1667054866 o.jpg" />
      <page pageid="122" ns="6" title="Arquivo:734703 10151384319616322 794864578 n.jpg" />
      <page pageid="705" ns="6" title="Arquivo:A1.png" />
      <page pageid="706" ns="6" title="Arquivo:A2.png" />
    </pages>
  </query>
</api>