Consider the the angles,
[tex]\angle5\text{ and }\angle7[/tex]
Let the angles between the above angles be,
[tex]\angle6\text{ }[/tex]
Then,
[tex]\begin{gathered} \angle6+\angle7=180\text{ (linear pair)} \\ \angle5+\angle6=180(linear\text{ pair)} \end{gathered}[/tex]
Therefore,
[tex]\angle6+\angle7=\angle5+\angle6[/tex]
So,
[tex]\angle7=\angle5[/tex]
