Answer:
He has 0 yards
Step-by-step explanation:
Initially he lost 10 yards
This means that he is 10 yards away from the starting point which we shall call origin
Afterwards, he gained 10 yards
what this mean is that he is back at the original point before the loss
Since he gained what he lost, then he is back at the origin and then we can say that no yards was lost or gain so we have him gaining 0 yards only
