To factor 28c - 12 by finding the greatest common factor (GCF), we need to identify the largest factor that both terms have in common.
First, we can factor out a 4 from both terms, since 4 is a common factor of 28 and 12:
28c - 12 = 4(7c - 3)
Therefore, the GCF of 28c and 12 is 4, and we can write the polynomial as the product of 4 and the expression (7c - 3).