Question 403547
Area = Width x Length 

57 = W x L

W= 2L-4 

57 = 2L-4 x L
57 = 2L-4L
57 = 2L 
L = 57/2 = 28.5

To get W : 

57 = W x 28.5 
W = 57/28.5 = 2 

To check answer : 28.5 x 2 = 57 ( answer is correct)