math -
**Anonymous**,
To Factor:

1) Find the Greatest Common Factor

2) Solve the trinomial (if their is one)

3) Find the difference of perfect square (if their is one)

So: the factors of 18,9, and 7

18c: 1c,2c,3c,6c,9c,18c

9c: 1c,3c,9c

7c: 1c,7c

So the GCF is C