Question 722580
Use fundamental relationships.  length*width is area for a rectangle.  Perimeter of a rectangle is 2 times the sum of length and width.


In symbols, or variables, if L is length and W is width, then:
2L+2W=perimeter, and L*W= area.  


You are looking for area for your described rectangle.  Use perimeter to find your unknown x, and then use this in your calculation for area, L*W.