You have 

 apples left. 
You have 5 whole apples, you took one whole apple out, which equals 4 whole apples left. Then with the whole apple you took out, you ate 

 of it. 
Jack ate  of an apple in 5 apples.
 of an apple in 5 apples. If you say that Jack ate 

 of 3 apples, then he ate 

 apples. So there isn't any difference when he ate 

 of an apple.
 
        
        
        
Answer:
complementary
Step-by-step explanation
Im not positive but theres a high chance its B
 
        
             
        
        
        
The answer for this question is choice c. Memorization is not a good way to truly understand math. You want to understand the reasoning behind your answers always. 
 A math expert is what you should strive to be! The first two choices are great ways to become this.
        
                    
             
        
        
        
3) an $8 delivery fee and $1.50 per litre of water
This is because the $8 is a constant baseline, then adding $1.50 times the amount of litres purchased.