Same-side interior angles where a transversal crosses parallel lines are supplementary:
The solutions to these equations can probably be done in your head:
- y = 180/(6+4) = 18
- x = (180-90)/5 = 18
The angles at the bottom of the figure, shown as different, are actually the same: 90°.
The angles at the top of the figure, shown as the same, are actually different: 108° on the left, 72° on the right.
