Answer:
x=4
Step-by-step explanation:
In a parallelogram opposite sides are congruent. That means BC and AD are congruent if ABCD must be a parallelogram.
[tex]6+3x=x+14\\6+2x=14\\2x=8\\x=4[/tex]
To double check you can substitute x into the equations again and check if they are equal.
[tex]6+3(4)=(4)+14\\6+12=18\\18=18[/tex]
