Given $x=4y$ and $y=2z$, which of the following expressions is equivalent to $x+4y-8z$ in terms of $z$ ?

$-3z$

$-2z$

$2z$

$4z$

$8z$

Approach

Write each variable in terms of $y$:

$$ x=4y, y=2z $$ $$ x=4(2z) $$ $$ x= 8z $$

Substitute:

$$ x+4y-8z $$ $$ (8z)+4(2z)-8z $$ $4 = \boxed{8z} $$