Okay... So firstly you need to expand 9 into the numbers inside the bracket. You'll get something like this. : 9z-27=12z...You want to make Z the subject so you shift it to the other side and it should be now like this : -27= 12z -9z(Remeber when shifted positive becomes negative and vice versa.)
so -27 =3z
And then you divide by 3 to get a single x.
And you'll get -9 as your answer.