Answer:
Yes, it does
Step-by-step explanation:
When we add a number to its additive inverse, the resulting value is zero
The first case is running up 10 flights which we consider positive
then he runs down 10 flights of stairs; this we can consider as - 10
So adding this together, we have -10 + 10 to give zero
What this mean is that we have added a number to its additive inverse
