Possessive nouns are used to indicate ownership.
Possessive nouns usually are formed by adding an apostrophe (') and s.
When a noun is plural and ends in s, just add an apostrophe (').
The kids' toys
My parents' house
The teachers' lounge
If two people own one thing, add the apostrophe and s to the second person only.
John and Mary's new house
David and Sue's wedding
Tom and Doug's car
If two people own separate things, add the apostrophe and s for each person.
Susan's and Beth's books
Jean's and Dan's pants
Ben's and Jim's offices
Which of the following is not correct?
1) Dr. Hunts has a new computer.
2) Dr. Hunts's new computer is working well.
3) Dr. Hunts' computer is new.
4) Dr. Hunts old computer is not working.