Answer:
x = 13
Step-by-step explanation:
m∠ABC + m∠CBD = 180° {linear pair}
3x + 43 + 6x + 20 = 180
3x + 6x + 43 + 20 = 180
9x + 63 = 180
9x = 180 - 63
9x = 117
x = 117/9