example.php

<?php //Please do not include the opening PHP tag if you alreaddy have one

function mycustom_filter_gettext_with_context( $translated, $original, $context, $domain ) {

    if( $domain === 'event_espresso' ) {
        // This is an array of original strings
        // and what they should be replaced with
        $strings = array(
            'Attendee %d' => 'Participant %d',
            // Add some more strings here
        );
        // See if the current string is in the $strings array
        // If so, replace its translation
        if ( isset( $strings[$original] ) ) {
            // This accomplishes the same thing as _x()
            // but without running it through the filter again
            $translations = get_translations_for_domain( $domain );
            $translated = $translations->translate( $strings[$original], $context, $domain );
        }
    }
 
    return $translated;
}
add_filter( 'gettext_with_context', 'mycustom_filter_gettext_with_context', 10, 4 );