In the figure, ∠4 is an exterior angle to AUL.
∠4 = 77°
∠4 = ∠1 +∠2
∠1 +∠2 = 52° +25° = 77°
Substitute the value that we alreay know to find ∠3.
⇒ 77° + ∠3 = 180°
⇒ ∠3 = 180° - 77° = 103°
∠4 is equal to the measures of two nonadjacent interior angles, the sum of angles is always 180° so ∠1 +∠2 + ∠3 = 180°. In summary ∠4=sum of the measures of the two nonadjacent interior angles.
Hope this helps, have a BLESSED AND WONDERFUL DAY! As well as a great Black History Month and Valentine's day! :-)
- Cutiepatutie ☺❀❤