Answer:
212.5ft^2
Explanation:
First, go ahead and find the area of the total square. To do this, multiply the length by the height (15*15) to get 225. This is not our final answer, but it will help us solve the problem later.
Next, we need to find the area of the lower-left triangle that is cut off. To do this, we will find the side lengths of just that section. Because the left side of the square and the right side are the same total length, we can just subtract 10 from 15 to get a length of 5.
Now, to find the area of the triangle we will use b*h/2:
5*5/2=12.5
All that's left is to subtract this area from the initial area (225) to get our final answer of 212.5ft^2.