Question

como se arma essa conta 8+2x=-4-x

Answer 1

$8+2x=-4-x\to \\\\ 2x+x=-4-8\to \\\\ 3x=-12\to \\\\ x=-~ \dfrac{12}{3} \to \\\\ \boxed{x=-4}$

Answer 2

2X + X = - 4 - 8 
3X = - 12
 X = - 12/3
 X = - 4