Answer: A=302.85.
Step-by-step explanation:
We get the little part on the left side by doing Pythagoras: square root of c^2-a^2= 12.65.
We then get the bottom side of the large triangle 21+12.65=33.65. we then do 33.65*18*0.5 to get the total area, which is 302.85 (A=0.5*ground*height)
