Answer:
The value of x is 15.
Explanation:
As given
AD and BC are parallel .
Thus ABCD is a parallelogram.
Now by using the parallelogram property.
Consecutive angles are supplementary i.e ∠A + ∠B= 180°
As shown in the figure
∠A = (3x - 15 )°
∠B = (9x + 15 )°
Put in the above
3x - 15 + 9x + 15 = 180
12x = 180

x = 15
Therefore the value of x is 15.