Remember that
In a rectangle
opposite sides are parallel and congruent and the measure of the interior angles are 90 degrees
The diagonals are congruent
so
PS=ON
PO=SN
PN=OS
equate the equations of diagonals
PN=2x+5
OS=3x-2
2x+5=3x-2
solve for x
3x-2x=5+2
x=7
Find out PS
Remember that
PS=ON=x+3
substitute the value of x
PS=7+3