#### Answer

$|-8i|=8$

#### Work Step by Step

The absolute value of a complex number
$z=a+bi,$ denoted $|z|,$ is a nonnegative
real number defined as $|z|=\sqrt{a^{2}+b^{2}}$.
$|z|=|-8i|$
$=\sqrt{a^{2}+b^{2}}\qquad$ ...substitute $0$ for $a$ and $-8$ for $b$
$=\sqrt{0^{2}+(-8)^{2}}\qquad$ ...simplify.
$=\sqrt{0+64}$
$=\sqrt{64}\qquad$ ...evaluate.
$=8$