WP changes X to multiplication symbol!

Huh. That one rarely comes up.

Edit wp-includes/formatting.php.

In the wptexturize function, at about line 23, you’ll find these two lines:

$dynamic_characters = array('/\'(\d\d(?:’|\')?s)/', '/(\s|\A|")\'/', '/(\d+)"/', '/(\d+)\'/', '/(\S)\'([^\'\s])/', '/(\s|\A)"(?!\s)/', '/"(\s|\S|\Z)/', '/\'([\s.]|\Z)/', '/(\d+)x(\d+)/');
$dynamic_replacements = array('’$1','$1‘', '$1″', '$1′', '$1’$2', '$1“$2', '”$1', '’$1', '$1×$2');

The very last section in each one is what is doing the replacing you are describing. Change them to these to eliminate that:

$dynamic_characters = array('/\'(\d\d(?:’|\')?s)/', '/(\s|\A|")\'/', '/(\d+)"/', '/(\d+)\'/', '/(\S)\'([^\'\s])/', '/(\s|\A)"(?!\s)/', '/"(\s|\S|\Z)/', '/\'([\s.]|\Z)/');
$dynamic_replacements = array('’$1','$1‘', '$1″', '$1′', '$1’$2', '$1“$2', '”$1', '’$1');

All I did was to remove the last entry in each array. Remove those and you’re good.

I copy-pasted the code you posted

Well, don’t do that. Edit the code yourself, like I explained in the text above.

Copy and pasting code is not guaranteed to work in this case. This is because of the amp characters.

Just edit those lines in a normal text editor (Notepad will work) and remove the bits I mentioned.

Specifically, remove:
, '/(\d+)x(\d+)/'

and
, '$1& #215;$2'

I still get the same Parse Error

Well, you’re not editing anything anywhere near line 98, so that doesn’t make any sense.

Start with a fresh unedited copy of the file. Download the WordPress.zip again if you have to.

Use a very basic text editor. Notepad. TextPad. Not Word or anything else. Other editors can do things that basic simple text editors do not.

Other than that, I don’t know what to tell you. The instructions I gave work. I tested it just now.