a) Given
 Total area = 81 feet squared.
 Let the area of the square mat = x feet.
 From question, area of the rectangular mat is twice that of square mat.
  So, the area of the rectangular mat  feet.
 feet.
Now,
Total area = 81 feet squared
Then,
       
 Hence  the area of the one rectangular mat = 2*9 = 18 feet squared
b) Let the width of the rectangular mat = y feet.
   Then length of the mat = 2 y feet.
    Area of the rectangle 
    and area of rectangle = 18 feet squared.
    So, 
  
Width can not be negative.
Hence, the width of the rectangular mat = 3 feet
and  length of the rectangular mat = 3*2 = 6 feet