Answer: x = 6
Step-by-step explanation:
All angles in a triangle = 180*
9x - 11 + 80 + 57 = 180
9x + 137 = 180
9x = 54
x = 6
Plug in to see if its correct
9 (6) - 11 + 80 + 57 = 180
54 + 126 = 180
180 = 180
