back-of-an-envelope是什么意思，back-of-an-envelope的翻译，back-of-an-envelope音标、读音、用法和例句

Warning: file_put_contents(): Only 0 of 6032 bytes written, possibly out of free disk space in /home/www/wwwroot/zidian/201990.com/index.php on line 55
back-of-an-envelope是什么意思，back-of-an-envelope的翻译，back-of-an-envelope音标、读音、用法和例句_耀久九英英词典