what is the value of x in trapezoid abcd

Answer:
x=15
Step-by-step explanation:
Because CD║BA and BC≡AD,
Then: ∠B=∠A and ∠C=∠D.
All for corners must add up to 360°:
∠A + ∠B + ∠C + ∠D = 360
2∠B + 2∠D = 360
2(3x) + 2(9x) = 360
6x + 18x = 360
24x = 360
x = 15