Answer 1

If you are doing this within the main function then there should be another <x> variable declared outside main function as a global variable. The :: is known as scope resolution operator, it clearly defines from where the said variable <x> is to be read from, in the case where there are multiple variables declared by the same name.

You can see scope resolution operator explanation on the 3rd slide on this C++ course chapter:
https://www.sololearn.com/learn/CPlusPlus/1955/?ref=app

Hth, cmiiw