Answer:
She needs to run down 4.5 flights of stairs to represent an additive inverse
Step-by-step explanation:
Having an additive inverse means that she will be back at point zero.
The point zero in this context simply refer to her starting point.
So if she has run up 4.5 flights of stairs, then to be back at her starting point, she needs to run down also 4.5 flights of stairs