192 ft.
We can start by finding the area of the whole shape. 18*12= 216
Then we can see that the shape cut out has a length of 6 and the missing 8 from the 10. so 6*8= 48 and we cut 48 in half since the small shape was cut in half and get 24. So 216-24= 192ft
If you don't get it tell me, it is hard to explain.