Answer:
69°
Explanation:
All angles in a triangle must add to 180°:
(5x+9)+(4x+15)+(x+36)=180
10x+60=180
10x=120
x=12°
The problem asks for the measure of angle C:
C=(81-x)°=69°
You were on the right track because you got the value of x correct. You just didn't answer the problem correctly.