Question 958726
Let the angle B be x.
As per the problem angle A=x+20,
And angle C=x+x+20/2
A+B+C=180°(angle sum property of ∆)
x+20+x+(2x+20/2)=180°
After solving left hand side we get 4x+40+2x+20.    6x+60
                                     ----------- =  ------=180°
                                         2.           2
6x+60=180*2
6x+60=360
6x=360-60
6x=300
x=300/6
x=50°
Angle A=x+20=50+20=70°
Angle B=x=50°
Angle C=x+x+20/2=(70+50)/2=120/2=60°
Therefore 70+50+60=180°
Hence proved.