Actually Welcome to the Concept of the Angles.
Complementary angles are those which add up to get 90° , hence here
1.) 90-80 = 10° , 10 is complement of 80
2.) 90-(-120) = 210 , hence 210° is complement of -120
3.) 90-400 => 360°
4.) 90-95 = -5°
5.) 90-5 => 85°
6.) 90-(-35) = 125°
7.) 90-8 = 72°
all are the complement angles above.