Answer:
[tex]\large\boxed{x=\dfrac{a}{2+6z}}[/tex]
Step-by-step explanation:
[tex]2x+6xz=a\qquad\text{distributive}\\\\x(2+6z)=a\qquad\text{divide both sides by}\ (2+6z)\neq0\\\\x=\dfrac{a}{2+6z}[/tex]