I think B is alone sufficient to answer the question
As for the basic principle for a polygon to be a triangle is that sum of 2 sides is greater than the third side and difference of the 2 sides is always less than the 3 rd side.
So if angle B=80
This puts a limit on the other two angle(supposed x and y) to be between the range of 11-89 degrees.
Hence all the angles would be less than 90 degrees.
Kindly explain if this doesn't makes sense
As for the basic principle for a polygon to be a triangle is that sum of 2 sides is greater than the third side and difference of the 2 sides is always less than the 3 rd side.
So if angle B=80
This puts a limit on the other two angle(supposed x and y) to be between the range of 11-89 degrees.
Hence all the angles would be less than 90 degrees.
Kindly explain if this doesn't makes sense
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