Step-by-step explanation:
[tex] \angle 1 [/tex] is the exterior angle of the given [tex] \triangle. [/tex]
Therefore, by remote exterior angle theorem.
[tex] \therefore \: m \angle \: 1 = 60 \degree + 63\degree \\ \\ \huge \red{ \boxed{\therefore \: m \angle \: 1 = 123 \degree }}[/tex]
