Объяснение:
x:y=3:5, z=0,5(x+y)
x+y+z=180°
z+2z=180°
3z=180°
z=60°
x:y=3:5⇒x=3k; y=5k
x+y=180°=z=180°-60°=120°
3k+5k=120°
8k=120°
k=15°
x=3k=45°, y=5k=75°
