tentukan besar A dan C

Segitiga ABC
<A + <B + < C = 180°
30° + 4x + 8x = 180°
12x = 180° - 30°
12x = 150°
x = 150°/ 12
x = 12,5

<B = 4( 12,5) = 50°
<C = 8(12,5) = 100°