Please find the attachment.
We have been given that [tex]m\angle6=m\angle8[/tex] and b||c.
Let us match the reasons with given statements in the proof.
Since we know that if two lines are parallel then corresponding angles will be equal. So by corresponding angles [tex]m\angle7=m\angle8[/tex].
By substitution we will get,
[tex]m\angle6=m\angle8[/tex]
[tex]m\angle7=m\angle8[/tex]
Therefore, [tex]m\angle7=m\angle6[/tex]
Since we know that if the alternate interior angles are equal, then lines are parallel.
Hence proved that a||b.
