A+B+C+D=360°
A/4=B/7=C/2=D/5 B=7A/4 C=2A/4=A/2 D=5A/4
A+7A/4+A/2+5A/4=360°
A+12A/4+A/2=360°
A+3A+A/2=360°
9A=720°
A=80°
B=7×80°/4=140°
C=80°/2=40°
D=5×80°/4=100°
A+B+C+D=360°
3A=12B=6C=4D B=3A/12=A/4 C=3A/6=A/2 D=3A/4
A+A/4+A/2+3A/4=360°
4A+A+2A+3A=1440°
10A=1440°
A=144°
B=144°/4=36°
C=144°/2=72°
D=3×144°/4=108°