Lines A and B are parallel. If Angle 4 is 100 degrees, then angle 1 is

`_________`

.Lines A and B are parallel. If Angle 4 is 100 degrees, then angle 1 is

`_________`

.Detailed Explanation

Two angles that form a straight line add up to 180 degrees. If Angle 4 is 100 degrees then Angle 1 must be 80 degrees.