Remember that all 3 angles added of a triangle is always 180°.
Now form an equation :
34° + (8x - 23)° + (8x - 23)° = 180°
34° + 8x - 23° + 8x - 23° = 180°
8x + 8x = 180° - 34° + 23° + 23°
16x = 192°
x = 192° ÷ 16
= 12
