I believe this would be 51
        
             
        
        
        
Plug in -3 for x
f(-3) = 2(-3) - (-3 + 6)
f(-3) = -6 - (3)
f(-3) = -9
Solution: f(-3) = -9
        
                    
             
        
        
        
Lets go step by step and factor out each as we go
first lets factor out a 3 since 3 is common in 9 and 3 
3(3ab^2 - abc) 
now lets factor out a since its common in both 
3a(3b^2 - bc) 
now lets factor out a b since its common in both 
3ab(b - c) 
we can't factor anything else out so we are done.