Find the value of x for which ABCD must be a parallelogram.

Answer:
[tex]x=9[/tex]
Step-by-step explanation:
As a parallelogram has opposite sides parallel and equal.
Therefore, BC=AD
[tex]BC=16x-15[/tex]
[tex]AD=30+11x[/tex]
[tex]16x-15=30+11x[/tex]
Subtracting 11x both sides
[tex]16x-11x-15=30\\\\5x-15=30[/tex]
Adding '15' both sides:
[tex]5x=45[/tex]
Dividing by '5' both sides:
[tex]x=45/5\\\\x=9[/tex]
The value of 'x' is '9'