If the largest angle is 160 degrees, then the angle that it is 8 times larger than is equal to 160/8 = 20 degrees.
The sum of these 2 angles is 180 degrees which forces the third angle to be 0 degrees which is not allowed since each angle of the triangle has to be greater than 0 degrees.
So the largest angle has to be less than 160 degrees.
You will never be able to find the largest angle because, no matter how close you can get to 160 degrees, you will always be able to get a little closer.
It's simpler to say that the largest angle has to be smaller than 160 degrees.