Answer: x = 8
=================================================
Step-by-step explanation
Rule: The three interior angles of any triangle always add to 180
Using that rule, we can say the following
(angle1)+(angle2)+(angle3) = 180
(6x-9)+(65)+(76) = 180
6x+(-9+65+76) = 180
6x + 132 = 180
6x = 180-132
6x = 48
x = 48/6
x = 8
This x value leads to 6x-9 = 6*8-9 = 48-9 = 39
The three interior angles of the triangle are: 39, 65, 76
They add to 39+65+76 = 180, which confirms our answer.