Question 320945
Perimeter of a rectangle = 2(length + width) = 28 cm.
                            (length + width) = 28/2 = 14cm
Now since it is given that the width is x, 

length + x = 14

or, length = 14 - x

Area = length X width
     = (14 - x) X x
     = x(14-x)
     = 14x - x^2