single word requests - Adjective describing possession by someone else

Is there any adjective in English that would describe a quality of belonging or being in the possession of someone else who is not the speaker?

In short, what adjective would you substitute for the words in bold below:

What's inside of this bag?

I don't know. This is not my bag.

or

What's inside of this bag?

I don't know. This bag is not mine.

or

Jack, don't touch that toy car.

Why?

Because that toy is not yours.

Answer

I'd probably use somebody else's.