Answer:
93°
Explanation:
By exterior angle theorem:
(4x + 9)° = 2x° + (3x - 12)°
(4x + 9)° = (2x + 3x - 12)°
(4x + 9)° = (5x - 12)°
4x + 9 = 5x - 12
4x - 5x = - 12 - 9
-x = - 21
x = 21
Measure of exterior angle
= (4x + 9)°
= (4*21 + 9)°
= (84 + 9)°
= 93°