How far below zero is - 16 degrees Celsius?

16C

Step-by-step explanation:

The sentence "how far" refers to how separated is the value of - 16C from 0C, which means we need to calculate this using absolute values. These values must be always positive, because we only care for the separation between them. This separation will then be |-16C-0C|=16C, as is obviously expected, these 2 temperatures are separated by 16C, that is how far below 0C is - 16C.