Angles ABC and DBC make up a flat angle. Determine the type of angle DBC, if angle ABC: 1) acute 2) straight 3) obtuse

Since the unfolded angle is 180 °, the angle ABC + angle DBC = 180 °. Therefore:
1) if the angle ABC is acute, then its value is less than 90 °, then the value of the angle DBC will be more than 90 ° and it will be obtuse,
2) if the angle ABC is straight, then its value is 90 °, then the value of the angle DBC = 180 ° -90 ° = 90 ° and it will be straight,
3) if the angle ABC is obtuse, then its value is greater than 90 °, then the value of the angle DBC will be less than 90 ° and it will be sharp.