we know that
If the parallelogram ABCD is a rectangle
then
[tex]BD=AC\\AC=AX+CX\\AX=CX[/tex]
so
[tex]2CX=BD[/tex] ------> equation A
Substitute the given values in the equation A
[tex]2(3y-4)=2y[/tex]
Solve for y
[tex]6y-8=2y[/tex]
[tex]6y-2y=8[/tex]
[tex]y=2[/tex]
therefore
the answer is
[tex]y=2\ units[/tex]
