Explanation:
Rectangle ABDE is 4 units across the horizontal, and 2 units tall.
The area of this rectangle is length*width = 4*2 = 8 square units.
Triangle BCD has a base of 4 and height 2. The area of which is base*height/2 = 4*2/2 = 4 square units.
The total area is
rectangle + triangle = 8 + 4 = 12 square units
