tolong jawab nomor 18 pake cara please!!

∠CBD = ∠CAB + ∠ACB
2x + 3 = (x + 9) + 30
2x + 3 = x + 39
2x-x = 39-3
x=36

jadi ∠CBD = 2x+3
2(36) + 3 = 75°