Final answer:
To rewrite the sum as a product of the GCF and a new sum, we find the GCF of 3 and 15, which is 3. The correct answer is 3(X + 5).
Step-by-step explanation:
To rewrite the given sum as a product of the greatest common factor (GCF) and a new sum, we need to find the GCF of 3 and 15. The GCF of 3 and 15 is 3. So, we can write the sum as 3(X + 5). Therefore, the correct answer is option A, 3(X + 5).