Step-by-step explanation:
[tex]\angle{1} = 77°[/tex] because they are vertical angles.
The 77°-angle is supplementary with [tex]\angle{2}[/tex] therefore
[tex]77° + \angle{2} = 180° \Rightarrow \angle{2} =180° -77° = 103°[/tex]
[tex]\angle{3}[/tex] and [tex]\angle{2}[/tex] are vertical angles so
[tex]\angle{3} = \angle{2} = 103°[/tex]
