Why n * 180 degrees - (n-2) × 180 degrees = 360 degrees Help me

Why n * 180 degrees - (n-2) × 180 degrees = 360 degrees Help me

It's simple:
N * 180 degrees - (n-2) × 180 degrees
=N * 180 degrees - n × 180 degrees + 2 × 180 degrees
=360 degrees
If you have any questions, you can ask me again_ ∩)O.