Additional information: The diagram shows a rhombus PQRS. Calculate the values of x and y.

Can I assume that both are isosceles triangle? Even if it is, I calculated and found out that the answers are not constant

How should I go around to solve this?

Thanks

P.S Sorry that the picture is blurred, but the numbers are, "5x-20", "2x+13", "3x", "y".