Answer:
C and D
Step-by-step explanation:
in equations y=4x+9 and y=4x-9 you have the same slope (4) so paralleling is guaranteed.
y=9 and y=18 you can understand as y=0x+9 and y=0x+18, so in this situation you have the same slope (0), so lines y=9 and y=18 are parallel too.
 
        
             
        
        
        
36% is the answer to the question
        
                    
             
        
        
        
Let 

then you will have a^2-12a+36=0 and then you can just factor to find a
 
        
        
        
  hope it helps you friend....!!
:) 
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