Pls help me asap important assessment

Answer:
x-6
Step-by-step explanation:
The mistake when expanding the bracket 3(x-6),3 was supposed to multiply 6 but instead it was added to 6 instead
the correct working
3(x-6)+(4x+12)-6x
3x-18+4x+12-6x
(3x+4x-6x)+(-18+12)
=x-6