Answer:
29
Step-by-step explanation:
To find what isn't a composite number, we need to find which of these is prime. 27 isn't since its 9*3. 28 isn't since its 14*2. 29 is prime
27 has factors of 9 and 3, so it is composite.
28 had factors of 2, 4, 7, 14, so it is composite.
29 is prime, so it is the answer.
