| - 8 | means that -8 is 8 units far away from 0.
We use the units to answer, so we say that | - 8 | = 8.
The Absolute Value has defines and they are for basics.
[tex]|a| = a\\|-a| = a\\-|a|=-a\\-|-a|=-|a|=-a[/tex]
These are just basics for absolute value.
Therefore, | - 8 | = 8.