Explanation:
✧

- Set up an equation and solve for x :
⋆
[ Exterior angle is always equal to the sum of two non - adjacent interior angles ]
~Remove the unnecessary brackets
⟶

~Add the like terms : 2x ° & 3x°
⟶

~Move 4x to right hand side and change it's sign
~Similarly move 12 to left hand side and change it's sign
⟶

⟶

⟶

- Now , Substituting the value of x in (4x+9)° [ Exterior angle ]
⤿

☥

Hope I helped ! ツ
Have a wonderful day / night ! ♡
❅ Let me know if you have any questions regarding my answer! ❅
☞
!! ✎
▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁