Answers

2014-07-27T14:21:25+05:30
As the angles are in a ratio 
the angles are  3x  ,4x , 5x
mean=3x+4x+5x/3=12x/3=4x=80  (80 is the mean given)
x=80/4=20
the angles are 3*20=60
4*20=80
5*20=100
forth angle is 360-(60+80+100)=360-240=120

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