Why can’t customize format for pre tag?

cd /var/www/html/wp-content/themes/
sudo mkdir twentyfourteen-child
cd twentyfourteen-child
sudo touch style.css
sudo touch functions.php

sudo vim functions.php
<?php
function my_theme_enqueue_styles() {

$parent_style = ‘twentyfifteen-style’; // This is ‘twentyfifteen-style’ for the Twenty Fifteen theme.

wp_enqueue_style( $parent_style, get_template_directory_uri() . ‘/style.css’ );
wp_enqueue_style( ‘child-style’,
get_stylesheet_directory_uri() . ‘/style.css’,
array( $parent_style ),
wp_get_theme()->get(‘Version’)
);
}
add_action( ‘wp_enqueue_scripts’, ‘my_theme_enqueue_styles’ );
?>

sudo vim style.css
/*
Theme Name: Twenty Fourteen Child
Theme URI: https://example.com/twenty-fifteen-child/
Description: Twenty Fourteen Child Theme
Author: John Doe
Author URI: https://example.com
Template: twentyfourteen
Version: 1.0.0
License: GNU General Public License v2 or later
License URI: https://www.gnu.org/licenses/gpl-2.0.html
Tags: light, dark, two-columns, right-sidebar, responsive-layout, accessibility-ready
Text Domain: twenty-fourteen-child
*/
pre{
font-family:inherit;
font-size:16px;
border:1px solid red;
}

sudo service restart apache2
sudo service restart mysql

To open a post in my wordpress,the border turned into red color,
why the font-size in pre isn’t 16px?