Question - Multiple packages depend on one package but different version

This is not an issue but a general question.
What will happen if there are multiple packages depend on one same package but in different version? For example, I use package A and B in my app. Package A uses package C version1.0 but Package B uses package C version 2.0?

This is a general question for meteor package system and NPM package system.

Got response from @abernix

For Meteor, the answer is provided in the Meteor Guide section on version constraints:

you can never have two different versions of the same package loaded side-by-side in the same app

@abernix So what should we do if we face this kind of issue?