The sum of any triangle’s 3 angles should always add up to 180 degrees.
9x + 6x + 5x = 180
Combine the like terms
20x = 180, x = 9
Now multiply it out
9(9) = 81 degrees
6(9) = 54 degrees
5(9) = 45 degrees
The top angle = 81 degrees
The angle on the left = 54 degrees
The angle on the right = 45 degrees