Find the measure of the exterior angle.

Option (C)

Step-by-step explanation:

By the property of an exterior angle,

Exterior angle of a triangle is equal to the sum of two opposite interior angles.

(15x + 34)° = 29° + (12x + 26)°

15x + 34 = 29 + 12x + 26

15x - 12x = 55 - 34

3x = 21

x = 7

Measure of exterior angle = (15x + 34)°

                                           = 15(7) + 34

                                           = 105 + 34

                                           = 139°

Option (C) is the answer.