We use "~죠(지+요)" when we trying to say "~지" politely.
And the use of "~지" is coming as below.
We use "~지?" when we ask someone assuming that he/she already did it.
Second, we use "~지" when we answer to a question with an intension to let him/her to know that we surely did it.
For example:
"점심식사하셨죠?" "You had lunch, right?"
"네, 맛있게 먹었죠." "Yes, I did of course."
And finally, we rarely use "~지?" When we tell someone to do something with sarcastic remarks.
For example: "점심밥이나 먹지?" "Why don't you just eat(finish) your stupid lunch?"