Answer:  An expression for the length of bed D is 

The length of bed D= 4.7 ft
Explanation:
Given: Bed A is seven feet long. 
⇒ The length of bed A= 7 ft.
Bed B is 7/8 of bed A.
⇒ The length of bed B = 

 Bed C is 7/8 of bed B. 
⇒ The length of bed C= 

Bed D is 7/8 of C. 
⇒ The length of bed D=  

