a+b+c+d=360 (grade )
a/1/2=b/1/3 =c/1/6 =d /1/7
a+b+c+d /1/2+1/3+1/6+1/7 =360/21+14+7+6/42=
360/48/42 =360*42/48 = 315
a/1/2 =315 ;a=315*1/2 =157.5 gr.
b/1/3 =315 ;b =315/3 =105 gr.
c/1/6 =315 ;c =315/6 =52.5 gr
d /1/7 =315 ; d =315/7 =45 gr
(V : 157.5+105+52.5+45 =360 grade)