Answer:
258 ft
Explanation:
seperate the polygon into two boxes that way u have one big box that is 21 ft in width and 8 ft in height. Then multiply 21*8 to find the area of the box which is 168.
for the other box you can find the height by subtracting 18 ft and 8 ft from the first box which gives a height of 10 ft. To find the wisth you have to subtract 21-12 which is 9. Now you can multiply 10*9=90
Add the two boxes together:
90+168=258