The rotten tried to make my work tougher

The boss asked me to help that rotten guy who worked under me to complete his work. After 3 hours I finished the task. But he could still read some stupid online novels when he could not finish his work.

Boss asked both of us to see him, when the boss has two tasks on hand. He asked "which task will you handle?" That rotten guy quickly answered and said he would take that task(easy task=less time to complete). Then the boss paused, and asked him to do the other one(the tough work which I don't like it, eventhough I can finish it very fast. It wasn't my part also anyway). Thank god it countered back. So the boss asked me to continue my work, searched YouTube videos and download. My YouTube day continues.... again...