Let the length and width of the rectangle be L and W.
The perimeter of a rectangle is 7 times its width.
=> 2L + 2W = 7W
=> 2L = 5W
=> L = (5/2)W
Area = 40
=> L*W = 40
=> (5/2)W*W = 40
=> W^2 = 16
=> W = 4
L = 10
The length of the rectangle is 10 and width is 4