Two angles are congruent if they are equal and supplementary if there sum is 180.
Given data:
c and d are parallel.
Now
[tex]\angle1,\angle3[/tex]are corresponding angles, so they are equal.
So,
[tex]\angle1,\angle3[/tex]form a congruent pair.
Now since
[tex]\angle1=\angle6[/tex]since they are vertically oppsoye angles.
And,
[tex]\angle1=\angle3(\text{corresponding angles)}[/tex]So,
[tex]\angle6=\angle3[/tex]So,
[tex]\angle6,\angle3[/tex]form a congruent pair.
Now,
[tex]\begin{gathered} \angle3=\angle8(vertically\text{ opposite angles)} \\ \angle1=\angle3(corresponding\text{ angles)} \\ \Rightarrow\angle1=\angle8 \end{gathered}[/tex]So,
[tex]\angle1,\angle8[/tex]form a congruent pair.
[tex]\angle7=\angle4(vertically\text{ opposite angles)}[/tex]So,
[tex]\angle7,\angle4[/tex]form a congruent pair.
Now,
[tex]\angle1+\angle2=180(linear\text{ pair)}[/tex]So,
[tex]\angle1,\angle2[/tex]form a supplementary pair.