Okay so you split 9ab + 12ax - 6b - 8x
into two 2-term polynomials
+ 12ax + 9ab and - 6b - 8x
doesn't look that good to me so lest try other one :
9ab + 12ax and - 6b - 8x
looks good for now
Pull out from each binomial separately
9ab + 12ax = 3a • (3b + 4x)
- 6b - 8x = - 2 • (3b + 4x)
Add up to arrive at the desired factorization so now you have
(3a - 2) • (3b + 4x)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Hope that Helped!