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.
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