Flipping something 180 degrees (doesn't matter if clockwise or counterclockwise) will always flip that thing upside down.
Your answer is 180 degrees.
Now, the reason why it's not 270 degrees clockwise because that's pretty much turning that 90 degrees counterclockwise. And 90 degrees is about how much a car does when making a left or right turn.
Have an awesome day! :)
