Given:
We're given a four-sided figure.
Value of ∠ADB = 9x + 20
Value of ∠DBC = 15x + 2
To find:
The value of x for which ABCD must be a parallelogram.
Step-by-step solution:
For ABCD to be a parallelogram, Alternate angles (Z angles) should be equal:
Thus,
∠ADB = ∠DBC
9x + 20 = 15x + 2
18 = 6x
x = 3
Final answer:
Thus we can say that the value of x should be 3 for ABCD to be a parallelogram.