Question 57084
Call the length = x
Call the width = y 
You know that x*y = 48
You also know that x = 3y - 8 
Substitute this x in x*y=48 to obtain: 
y * (3y-8) = 48 
3y² - 8y - 48 = 0
Now solve this for y (delete the negative root)
Solution: y = 4/3 + 4*sqrt(10)/3 

          x = 48 / (4/3 + 4*sqrt(10)/3)