Match nth item of a string

[Joep]

I'm looking for a way to grab the value of the 3th parent and 2th child item of a string. Below an example of the data i get. The value i need is marked in red. It's not possible to use the id's as they change all the time. With css it's done like this item:nth-child(3) item:nth-child(2) but how is it done in Lua?

<values>
  <item id='0x8764bc'>
      <item id='0x87676c'>
        <value>32.5°C</value>
      </item>
      <item id='0x87de1c'>
        <value>28.6°C</value>
      </item>
      <item id='0x87de64'>
        <value>28.4°C</value>
      </item>
      <item id='0x876724'>
        <value>62.7°C</value>
      </item>
  </item>
  <item id='0x876504'>
      <item id='0x8b7ab4'>
        <value>Aan</value>
      </item>
      <item id='0x87e0d4'>
        <value>Aan</value>
      </item>
  </item>
  <item id='0x8765dc'>
      <item id='0x878554'>
        <value>Uit</value>
      </item>
      <item id='0x861b84'>
        <value>Aan</value>
      </item>
      <item id='0x861bcc'>
        <value>Aan</value>
      </item>
      <item id='0x87850c'>
        <value>Aan</value>
      </item>
  </item>
</values>