perhatikan gambar berikut

180° = 6x° + 20° + 2x°
180° = 8x° + 20°
8x° = 180° - 20°
8x° = 160°
x° = 160° : 8
x = 20°

ABD = 6x+20°
ABD = 6(20)° + 20°
ABD = 120° + 20°
ABD = 140°

Jawaban B.

6x +20 =180 + 2x
6x - 2x = 180 - 20
4x = 160
x = 160 : 4
x = 40