Answer:
The length of the pillow in the shape of a wedge is 4 ft.
Explanation:
The formula for the volume of a wedge is: 

Where b is the base, h is the height and L is the length. 
The volume of the pillow is: 

Then we equate both equations and obtain: 

We know b and h. So we cleared L. 

So 


 
 

The length of the pillow is 4 ft.