John injures his shoulder while lifting weights.  After the injury, his bench press goes down 80%.  After a bit of training, he manages to triple the weight he can bench.  If he started with a 500-pound bench press, what is it now?
He lost 500*.8=<T>multiply(500, 0.8)=400.0 pounds from his bench
So his bench went to 500-400=<T>subtract(500, 400)=100 pounds
After training it increased to 100*3=<T>multiply(100, 3)=300 pounds
