Question

If ab is parallel to cd and angle 1 = 130 degrees, find angle 2.

Answer 1

If you're referring to the attached illustration then angle 2 is 50 degrees.

To compute:
Angle 2 = 180 degrees - Angle 1
Angle 2 = 180 degrees - 130 degrees
= 50 degrees

Angles on a straight line always add up to 180 degrees. So to get the other half of the angle, just directly deduct the given angle (angle 1) from 180 degrees.