ANSWER
[tex]^{\boxed {}} = 4.[/tex]
EXPLANATION.
The given equation is
[tex] \boxed {}(x + 2) + 2x = 2(x + 6) + 4x[/tex]
Let us expand the right hand side to obtain:
[tex]\boxed {}(x + 2) + 2x = 2x + 12+ 4x[/tex]
We group similar terms and keep the expression with the box on the left.
[tex]\boxed {}(x + 2) = 2x - 2x+ 12+ 4x[/tex]
Simplify
[tex]\boxed {}(x + 2) = 4x + 12[/tex]
We can see that the value of box the will be the equation to have no solution is 4.
Let us substitute 4 for box.
[tex]4(x + 2) = 4x + 12[/tex]
[tex]4x + 8 = 4x + 12[/tex]
[tex]4x - 4x = 12 - 8[/tex]
[tex]0 = 4[/tex]
This is not true. Hence the equation has no solution when
[tex]\boxed {} = 4[/tex]