In the given figure, AB is parallel to CD. What is the value (in degrees) of angle BEC?

Correct option is C

Given:

AB ∥ CD

∠ABE = 100°

∠ECD = 150°

Find ∠BEC

Concept Used:

Angles on a straight line sum to 180°.

Parallel line angle property.

Formula Used:
Interior angle = 180° − (sum of adjacent acute angles)

Solution:

At point B:

Angle between BE and the straight horizontal line AB:

180° − 100° = 80°

At point C:

Angle between CE and the straight horizontal line CD:

180° − 150° = 30°

Now, at point E:

∠BEC = 180° − (80° + 30°)

= 180° − 110°

= 70°

Therefore,

∠BEC = 70°