download the twentytwelve theme here
http://wordpress.org/extend/themes/twentytwelve
unpack the files and take the page.php file and upload it to the wp-content/themes/twentytwelve folder overwriting the one that is there
download the twentytwelve theme here
http://wordpress.org/extend/themes/twentytwelve
unpack the files and take the page.php file and upload it to the wp-content/themes/twentytwelve folder overwriting the one that is there