help question is in attachment

Answer:
As the angles are supplementary, their sum is 180
123 + 3x = 180
3x = 57
x = 19
Answer:
x° = 19°
Step-by-step explanation:
[tex] = > 123 \degree + 3x \degree = 180 \degree \\ \\ = > 3x\degree = 180\degree - 123\degree \\ \\ = > 3x\degree = 57\degree \\ \\ = > x\degree = (\frac{57}{3} )\degree \\ \\ = > x\degree = 19\degree [/tex]