How to be expert in these kinda questions!

Thanks Melody!

You have to factorise this in pairs first up.  :)

I have numbered the rows for you. 

$$\\6xy - 4y \;\;\;+\;\;\; 6 - 9x\qquad \qquad\qquad (1)\\
=2y(3x - 2) \;\;\;+\;\;\;-3( -2 + 3x)\qquad (2)\\
=2y(3x - 2) \;\;\;+\;\;\;-3(3x-2)\qquad (3)\\
=(2y-3)(3x - 2)\qquad\qquad \qquad \qquad (4) \\$$