Question

​ Parallelogram ABCD ​ is a rectangle.

Answer 1

The diagonals are equal and they bisect each other.
BD=2BX=2(y+4)=2y+8
AC=BD
4y=2y+8
2y=8
y=4

Answer 2

I hope this helps you


AC=BD


BX=XD=AX=XC


AC/2=BX


4y/2=y+4


y=4