Answer:
x = 8 , ∠ ABC = 66°
Explanation:
From the diagram
∠ ABC + ∠ DBC = ∠ ABD ( substitute values )
9x - 6 + 2(x + 4) = 90 ← distribute parenthesis and simplify left side
9x - 6 + 2x + 8 = 90
11x + 2 = 90 ( subtract 2 from both sides )
11x = 88 ( divide both sides by 11 )
x = 8
Then
∠ ABC = 9x - 6 = 9(8) - 6 = 72 - 6 = 66°