Почему ошибка? И как её исправить?

Question

https://code.sololearn.com/c2SPwa8y367W/?ref=app

Answer 1

Hello Andrey ,
The `sum` function accepts 2 parameters and both have default value. The problem here is we are calling the function and supplying the second argument value (9 for <b>) - while at the same time we are skipping the first argument (value for <a>).
In short, an optional parameter cannot be skipped (a)when the next optional parameter (b) is given a value.
Sorry for reply in English, slow connection makes Google Translate hangs XD

Answer 2

Thank you very much