Practice!

Sample Problem

The figure is not drawn to scale.

∠DBC = 60°. What is ∠ABD?

∠ABD = °.

Solution

∠ABD and ∠DBC are angles on a straight line. Their sum is 180°.

∠ABD = 180° − ∠DBC = 180° − 60° = 120°

∴∠ABD = 120°