你的17定义的是字符串......把引号去了就行

age=('17')你这样给是字符串，正常会产生错误，如下not supported between instances of 'str' and 'int'，

改成age =17即可

Computer regarded your

『('17')』　of   『age=('17')』 as a 'string',not a 'number'.

So it's working like down here

else:

      print('adult')

If you change your code from

____________________________________

age=('17')      <-----------------------

if age<18:

  print('teenager')

else:

      print('adult')

____________________________________

to

____________________________________

age=17       

  <------------------------

if age<18:

    print('teenager')

else:

    print('adult')

____________________________________

That will  be correct.

Enjoy your coding.(^_^)