First, the area cannot be 15×8, or 120 cm^2, because this isn't a normal rectangle.
We can get our answer to what the length of the odd-looking lines are by seeing that the length of the top line of the cutout is equal to half of the 8 cm^2 line. Half of eight is four, so each line in the square cutout is a length of four.
So, our diameter is 15+8+8+4+4+4+4+4, or 52 cm^2.
Here is where even I'm getting stumped!
I think the answer is 100, because if you subtract 15×8=120 and subtract 4 (the length of the small sides) × 5 (the amount of them) you get 100 cm^2.
Try it, and see if it works!
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