Explanation:
If I plug x = 1 into the original equation
-6 + 2(1) = -4
It doesn't equal -10, so he is incorrect.
Why? I personally would have added 6 in the first step to get
2x = -4
Then dividing by 2, you get
x = -2
Now plugging that in
-6 + 2(-2) = 10