fix typo

git-svn-id: http://svn.linuxfromscratch.org/LFS/trunk/BOOK@1727 4aa44e1e-78dd-0310-a6d2-fbcd4c07a689

chapter07/hosts.xml

@@ -48,7 +48,7 @@ correctly.</para>
 
 <para>Of course, the 192.168.1.1 and www.mydomain.org have to be changed
 to your liking (or requirements if assigned an IP-address by a network/system
-administrator and this machine is planned to be connected to am existing
+administrator and this machine is planned to be connected to an existing
 network).</para>
 
 </sect1>