780-200:[5.6-4[a:2-1]=770-18 780-200:[5.6-4[a:2-1]=752 780-200:[5.6-4[a:2]=752+1 780-200:[30-4a:2]=753 580:[30-4a]=753.2 580:[30-4a]=1506 580:30=1506+4a 19,333=1506+4a 19,333-1506-4a=0 -1486,66-4a=0 -4a=1486,66/[-1] 4a=-1486,66 a=-1486,66:4 a=-371,665