The area of the polygon can be calculated by breaking it down into smaller shapes. The polygon resembles the letter "H" with an outer rectangle and two smaller rectangles inside.
The area of the outer rectangle is:
Length x Width = 12 x 3 = 36 square units.
The area of the upper smaller rectangle is:
Length x Width = 12 x 5 = 60 square units.
The area of the lower smaller rectangle is:
Length x Width = 12 x 6 = 72 square units.
Adding up these areas gives us:
36 + 60 + 72 = 168 square units.
Therefore, the area of the polygon is 168 square units.