need help with this problem! It isn't too hard, but still i dont get it :/

I did (217.2 - 238.4) / 2 on my calc and got -10.6.

Did i do something wrong?

No, you did it correctly    -10.6  is in thousands as the question stated....

Ohhh I see and it is a decrease, so the first option should be the correct answer I believe

Yeppers!