Explanation:
here's your solution
=> angle 3 and angle 8 are interior angles
we know that sum of both angle is 180°
=> angle 3 + angle 8 = 180°
=> angle 3 + 129° = 180°
=> angle 3 = 180° - 129°
=> angle 3 = 51°
now , angle 3 and angle 1 are vertical angle
hence both angle are equal
=> angle 1 = 51°
hope it helps 【€€】