Respuesta :

in a parallelogram, the adjacent angles are supplementary angles. Which means that their sum of the adjacent angle is equal to 180 degrees  
A + B = 180
(9x + 15) + ( 3x -15) = 180
12x = 180
X = 180/12
X = 15

Answer:

The value of x is 15.

Step-by-step 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

[tex]x = \frac{180}{12}[/tex]

x = 15

Therefore the value of x is 15.