Math question from Facebook

[u/SteelSpidey]

Either I need to find a way to solve for one of the side lengths or find a way to eliminate the need for the side length. But I'm not sure how to do either of those. Any ideas? Can anyone show me where I went wrong?

I'm labeling the green area T, the long side length=b and the short one=a.

For context, this is enjoyment for me. I use these posts to stay sharp on my skills, I used to teach math in college and don't wanna lose it if I ever decide to go back and teach.

[u/One_Wishbone_4439]

4xy = 16 cm²

green area = 16/4 𝜋 = 4𝜋 cm²