Day 20 is the last training day of Week 3, and you've definitely earned a break. You'll get tomorrow off, so make sure you bring everything you have to today's workout.
The trisets you'll do today are a hybrid of core, shoulder, and cardio work. They'll punish any weakness you have and teach you what it means to push it. Move from one exercise to the next without rest until you've completed all three moves. Once you've done that, you can take a little breather.
One of the best parts of the Remix trainer is that you don't have to do any boring cardio. Mike has built all the conditioning you need right into the workouts. Your job is to keep the intensity high so your heart rate stays elevated.