Which pair of lines in Fig. are parallel? Give reason.
       

AB || DC and BC || AD.
∠ BAD + ∠ ADC = 115° +65°
                      = 180°
∴ ∠ BAD and ∠ ADC are supplementary angles.
AB and CD are two lines and AD is a transversal. One pair of interior angles on the same side of the transversal are supplementary.
∴ AB and CD are parallel lines.
|||y ∠ CBA + ∠ BAD = 65° +115°
                            =180°
∴ ∠ CBA and ∠ BAD are supplementary angles.
∴ BC and AD are two lines and BA is a transversal. One pair of interior angles on the same side of the transversal are supplementary angles.