take the breadth as x and accordingly length as (x+18)
the formula for finding the perimeter of a rectangle is 2(l+b) now put the correct values as shown in the picture and form an equation this way you will be able to find x which is the breadth and length Is 18 morethan breadth ,now as u have found both length and breadth go ahead and find the area whose formula is length×breadth
HOPE IT HELPS