Possession can be shown in various ways.
Examples:
The answer of Jane and Janet was correct.
Their answer was correct.
Theirs was the correct answer.
The book belonging to Jim is torn.
His book is torn.
His is the torn book.
Always remember that the pronouns theirs, its, ours, hers, and yours do not take an apostrophe (') before the -s.
Correct: This is theirs. Its paint is peeling off.
Incorrect: This is their's. It's paint is peeling off.