Question

write a letter of thanks to a stranger for returning back your bag containing some important document s

Answer 1

1 if u r a office worker:  Dear Stranger,

   Thank you for returning my bag. It had a lot of important documents.
 If you would not returned me that bag in office, boss would be really angry.

 Yours Sincerely

X.Y.Z.

2 if u r a school student: Dear Uncle,

Thank you for returning my school bag. If you wont return me, I could not study my papers.

Your sincerely,
X.Y.Z