Good Riddles

Question: You are a surgeon who has to perform 3 operations today, but you only have 2 pairs of gloves (a and b) to perform the operations. Each of the people you are performing surgery on are infectious so you cannot touch any of them or their bodily fluids and they can't touch each other's bodily fluids. How do you perform all 3 operations with only 2 pairs of gloves?

Question: Not chest or box is now discussed. Money can be held in it, but just as we test its metal, within it there is rust.

[What is it?]

Question: You can call me a home, but I have no doors.
Someone lives inside me, but leaves when there's no more.

What am I?

Question: What single line can you add to the following statement to make it true?

5+5+5=550

Question: Which comes first, chicken or egg?