Answer:
Step-by-step explanation:
The secret trick to factoring is the greatest common factor.
The greatest common factor of 9 and 21 is 3. Thus, our expression is
3(3 + 7).
The greatest common factor of 14 and 28 is 7. Our expression is
7(2 + 4)
The greatest common factor of 80 and 56 is 8. This makes our expression
8(10 + 7).
