Using "gettext" WordPress filter to change the string "Page ... of ..." of Rank Math plugin in the <title> tag.

gettext-filter-rank-math.php

<?php
/**
 * Change the string "Page ... of ..." of Rank Math plugin in the <title> tag
 *
 * @link http://codex.wordpress.org/Plugin_API/Filter_Reference/gettext
 * @link https://developer.wordpress.org/themes/basics/conditional-tags/#testing-for-paginated-pages
 * 
 */
function my_text_strings($translated_text) {
	global $wp_query;
	$paged = $wp_query->get('page');

	if ($paged > 1 && $translated_text == 'Page %1$d of %2$d') {
		$translated_text = __('Página %1$d de %2$d', 'rank-math');
	}

	return $translated_text;
}
add_filter('gettext', 'my_text_strings', 20);