How is the area of a rectangle affected when its length is doubled and its width is

Question:

How is the area of a rectangle affected when its length is doubled and its width is halved?
How is the area of a triangle affected when its base is doubled and its height is halved? How are the area of a rectangle and triangle affected when their horizontal dimensions are multiplied by 3 and their vertical dimensions are multiplied by one-third? Do you think this relationship is true for any two-dimensional figure?