Add suggested 'The' at start of sentence

Co-authored-by: Hans Olsson <HansOlsson@users.noreply.github.com>

chapters/equations.tex

@@ -195,7 +195,7 @@ \subsection{If-Equations}\label{if-equations}
 
 \subsection{When-Equations}\label{when-equations}
 
-\lstinline!when!-equations\index{when@\robustinline{when}!equation}\index{then@\robustinline{then}!when-equation@\robustinline{when}-equation}\index{elsewhen@\robustinline{elsewhen}!when-equation@\robustinline{when}-equation} have the following syntax:
+The \lstinline!when!-equations\index{when@\robustinline{when}!equation}\index{then@\robustinline{then}!when-equation@\robustinline{when}-equation}\index{elsewhen@\robustinline{elsewhen}!when-equation@\robustinline{when}-equation} have the following syntax:
 \begin{lstlisting}[language=grammar]
 when expression then
    { equation ";" }