Answer:i think there was a pic to go with this to 
B(answer)
 
        
             
        
        
        
1/2 is the largest fraction out of all of them
        
             
        
        
        
18. S=r^2-t^2
 S+t^2=r^2
 r=sqrt(S+t^2)
20. Tan 18=x/12
 x=12×Tan 18
 x=3.899036355
 x=3.90
I hope this helps.
        
             
        
        
        
False because -21/-7=w is 3 and 3/-7 cannot be -21
        
                    
             
        
        
        
It’s B or D , im not that good but I don’t know , so try your best or take educated guess ( or ask a parent )