Which one of these numbers is a composite number: 17, 51, 97, or 89?
Composite numbers are divisible by 3 or more numbers.
17 is divisible by 1 and 17 only, so it's not composite.
51 is divisible by 1, 51, 3, and 17, so it's composite.
97 and 89 are divisible by two numbers only, so they are not composite.
So we conclude that the answer is
51
Good luck with your studies.