-6(1 + m) = -12
Multiply out the brackets:
So you get, -6(1 + m) = -12 = -6x1 + (-6)xm = -12
-6 -6m = -12
Then you can add 6 to both sides of the equation:
So, - 6 - 6m + 6 = -12 + 6
- 6m = - 6
Now you can divide both sides of the equation by -6:
-6m/-6 = -6/-6
So now the final answer is m = 1
(PS you can always check if you've got the right answer when you do this kind of thing by putting the answer that you get, i.e. in this case m=1, back into the original equation. So -6(1 + m) = -6(1 + 1) = -6 x 2 = -12 => which is the correct answer)