These first two characters are interpreted by the XML processor very early in the analysis of your source. So they need to be authored specially via the XML entities &amp; and &lt;. In practice, escaping > is rarely necessary. So fundamentally within PreTeXt there are just two characters to type carefully or exceptionally.
If you consistently follow the prescription in the previous paragraph you will avoid a descent into escape-character hell and avoid a lot of head-scratching. In particular, you should have no need of the <![CDATA[ ]]> mechanism of XML, so please just forget we even mentioned it. But see Subsubsection 4.1.4.2 if you are curious, or want a more thorough discussion.