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.
