Here is your answer
[tex]\bold{x=12}[/tex]
REASON:
[tex]<font color="blue" size=5>Concept used</font>[/tex]: The opposite sides of a parallelogram are equal.
So, in above given figure
[tex] 3x+7=5x-17 [/tex] (measures of opposite sides)
[tex] 5x-3x= 17+7 [/tex]
[tex] 2x= 24 [/tex]
[tex] x= 24/2 [/tex]
[tex] x= 12 [/tex]
HOPE IT IS USEFUL
