find the greatest common factor 28 and 12
use the GCF to factor 28+12.

Answer:
(a) 4
(b) 4 * (7+3)
Step-by-step explanation:
(a) Let's first start by prime factorizing (finding the prime factors) 28 and 12:
12: 2*2*3
28: 2*2*7
We can see here they both share a common factor of 2*2, which is 4, therefore the GCF is 4.
(b) Factor a 4 out from the equation:
[tex]4*(\frac{28}{4}+\frac{12}{4})[/tex]
This gives us:
4 * (7+3)