Respuesta :

Answer:

-4z-6y-9

Step-by-step explanation:

7z-[(2z+y)-(-5y+3z)+9]-12z

=7z-[2z+y+5y-3z+9]-12z

=7z-2z-y-5y+3z-9-12z

=7z-2z-12z+3z-y-5y-9

=-4z-6y-9