What you have to do is multiply 21 by 2. it is 42. $42 dollars was the original price of the bookcase.
 
        
             
        
        
        
Answer:
solution given:
balanced: C4H6O3 + H2O −−→2 C2H4O2
 
        
             
        
        
        
Its (-10,-4) because when you graph it you get (-10,-4) straight through the orgin
        
             
        
        
        
I think it's B because it contains the highest numbers