If both diagonals of a quadrilateral bisect each other when is the quadrilateral a parallelogram?

It is more than just a quadrilateral. In fact it is going to be hard to pick.

These facts suit a square,  a rectangle, a rhombus, and a parallelogram. And the above statement is true, but maybe a little harder to prove than the converse of the statement, which is the usual one you find.

The converse is "If you have a parallelagram, the diagonals bisect each other."

You might think a trapezoid deserves some mention. The diagonals of a trapezoid do not bisect each other.

The answer is: y would equal 3 because if you simplify the equation then it would be y= 3x+9 and if you divide 3x and 9 by 3 it would equal 3. y= 3