James has a room that is 13 feet by 18 feet.  He increases each dimension by 2 feet.  He then builds 3 more rooms of equal size and 1 room of twice that size.  How much area does he have?
He increases the length to 13+2=<T>add(13, 2)=15 feet
He increases the width to 18+2=<T>add(18, 2)=20 feet
So the rooms are 15*20=<T>multiply(15, 20)=300 square feet
So he has 1+3=<T>add(1, 3)=4 rooms of this size
So he has 4*300=<T>multiply(4, 300)=1200 square feet of rooms this size
He also has one room of size 300*2=<T>multiply(300, 2)=600 square feet
So he has 1200+600=<T>add(1200, 600)=1800 square feet of rooms
