The answer to the problem is b
        
                    
             
        
        
        
The graph should look the the one I attached to this answer
 
        
             
        
        
        
Answer:
He does not divide the numerator and the denominator by the same number. Nicholas divides 20 by 5 and 30 by 6. He ought to have divided 30 by 5 as well and then simplified.
P.S. Nicholas should have just divided both 20 and 30 by 10 to simplify in one step