Answer:
The mistake was -9, the answer is 1x -6
Explanation:
3 (x - 6) + (4x + 12) - 6x =
3x - 18 + 4x + 12 - 6x = (use distributive property for this step)
3x + 4x - 6x - 18 + 12 = (rearrange so like terms are easy to find)
1x - 6 (use addition and subtraction to get the final answer)
I hope this helps you :)