Answer:
184 ft
Explanation:
so, for this, the key is the smaller dimentions on the inside, they are the area of the smaller inner rectangle (416 ft) and the bigger dimentions on the outside, are for the entire rectangle including the mowed area (600 ft), but you dont know the exact value of the mowed area, so you would simply subtract the areas (600-416=184) and that number, 184, is the area of the mowed area that you didnt know.
hope this helps
kleann