〜において：　於（いて） 〜で：　在

Oh! Thanks for pointing out my mistakes! It helps a lot, thanks everyone.

体育館において is more formal than 体育館で, but not て. However, you can also say 体育館にて, they means the same. One more thing, いわれたisn't correct, 行われた is read おこなわれた, its dictionary form is 行う(おこなう). I hope this helps you.

I think it's same