If this was a colosseum type situation, the mammoth neg diffs. Even 100 gorillas could not take out a mammoth in this situation.
Just to highlight the folly of this event, I think it would be good to consider that even current elephants are over 100x stronger than an average human male... the only thing humans are 100x stronger than would be small rodents. But it's worse than that because even small rodents can bite through our skin, whereas we would break our teeth and jaw long before we could bite through a mammoth.
If humans have a wide open area and time to strategise a plan, then they could defeat the mammoth through exhaustion. But then, it wouldn't really be a fight, it would be a hunt. They would have to continuously pretend to attack and retreat over hours before it collapses from exhaustion and then rip off it's tongue or ballsack (which would still be really difficult and dangerous). In a situation like this, humans would take it high diff but with low casualties.