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>
    <allfileusages afcontinue="Cnt_inst_16.PNG|10" />
  </query-continue>
  <query>
    <allfileusages>
      <f fromid="146" ns="6" title="Файл:Bash highway to shell.jpg" />
      <f fromid="11" ns="6" title="Файл:Bash profile.PNG" />
      <f fromid="63" ns="6" title="Файл:Blkid iso.PNG" />
      <f fromid="93" ns="6" title="Файл:Chdir example.png" />
      <f fromid="10" ns="6" title="Файл:Cnt inst 0.PNG" />
      <f fromid="10" ns="6" title="Файл:Cnt inst 1.PNG" />
      <f fromid="10" ns="6" title="Файл:Cnt inst 12.PNG" />
      <f fromid="10" ns="6" title="Файл:Cnt inst 13.PNG" />
      <f fromid="10" ns="6" title="Файл:Cnt inst 14.PNG" />
      <f fromid="10" ns="6" title="Файл:Cnt inst 15.PNG" />
    </allfileusages>
  </query>
</api>