The equation: [tex]-2(x+3)=-2x-6[/tex], is simplified with distribution of parentheses: [tex]-2x-6=-2x-6[/tex].
Now add [tex]2x[/tex] to both sides and get: [tex]-6=-6[/tex].
The numbers are equal therefore the solution to the equation [tex]x[/tex] can be any number [tex]x\in\mathbb{R}[/tex].