According to the Exterior Angle Theorem, the measure of an exterior angle of a triangle is equal to the sum of the measures of the two nonadjacent interior angles. Let's write an equation applying this theorem.
29+(12x+26)=15x+34
We will now solve the above equation for x.
Once we know the value of x, we can substitute it to the expression of the exterior angle.
15x+34 → 15( 7)+34 → 139
Therefore, the measure of the exterior angle is 139^(∘).
