Question 895807
The fourth vertex could be almost anywhere in the quarter plane, specifically in the quadrant 1, and NOT on the x-axis nor y-axis.  Also,  you probably want  {{{x>=2}}} and {{{y>=3}}}.  In fact, the choices are greater than that, since you can allow for a concave quadrilateral, so ANY point chosen can be a possibility as long as it is not one of the three points you already gave.


As an example, (3,3) will work; as well as (2,3).